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Birgit Leitinger - One of the best experts on this subject based on the ideXlab platform.
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meeting report first Discoidin domain receptors meeting
Journal of Cell Science, 2020Co-Authors: Birgit Leitinger, Frédéric Saltel, Patrick Auguste, Christelle Liard, Virginie Rocher, Laurent Azema, David SantamariaAbstract:ABSTRACT For the first time, a meeting dedicated to the tyrosine kinase receptors DDR1 and DDR2 took place in Bordeaux, a famous and historical city in the south of France. Over the course of 3 days, the meeting allowed 60 participants from 11 different countries to exchange ideas and their new findings about these unique collagen receptors, focusing on their role in various physiological and pathological conditions and addressing their mechanisms of regulation and signalling. The involvement of these receptors in different pathologies was also considered, with emphasis on cancer development and potential therapeutic applications. Here, we summarize the key elements of this meeting.
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structure of the Discoidin domain receptor 1 extracellular region bound to an inhibitory fab fragment reveals features important for signaling
Structure, 2012Co-Authors: Federico Carafoli, Birgit Leitinger, Marie Cathrin Mayer, Kazushige Shiraishi, Mira Anguelova Pecheva, Lai Yi Chan, Erhard HohenesterAbstract:The Discoidin domain receptors, DDR1 and DDR2, are constitutively dimeric receptor tyrosine kinases that are activated by triple-helical collagen. Aberrant DDR signaling contributes to several human pathologies, including many cancers. We have generated monoclonal antibodies (mAbs) that inhibit DDR1 signaling without interfering with collagen binding. The crystal structure of the monomeric DDR1 extracellular region bound to the Fab fragment of mAb 3E3 reveals that the collagen-binding Discoidin (DS) domain is tightly associated with the following DS-like domain, which contains the epitopes of all mAbs. A conserved surface patch in the DS domain outside the collagen-binding site is shown to be required for signaling. Thus, the active conformation of the DDR1 dimer involves collagen-induced contacts between the DS domains, in addition to the previously identified association of transmembrane helices. The mAbs likely inhibit signaling by sterically blocking the extracellular association of DDR1 subunits.
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crystallographic insight into collagen recognition by Discoidin domain receptor 2
Structure, 2009Co-Authors: Federico Carafoli, Birgit Leitinger, Dominique Bihan, Stavros Stathopoulos, Antonios D Konitsiotis, Marc Kvansakul, Richard W Farndale, Erhard HohenesterAbstract:The Discoidin domain receptors, DDR1 and DDR2, are widely expressed receptor tyrosine kinases that are activated by triple-helical collagen. They control important aspects of cell behavior and are dysregulated in several human diseases. The major DDR2-binding site in collagens I–III is a GVMGFO motif (O is hydroxyproline) that also binds the matricellular protein SPARC. We have determined the crystal structure of the Discoidin domain of human DDR2 bound to a triple-helical collagen peptide. The GVMGFO motifs of two collagen chains are recognized by an amphiphilic pocket delimited by a functionally critical tryptophan residue and a buried salt bridge. Collagen binding results in structural changes of DDR2 surface loops that may be linked to the process of receptor activation. A comparison of the GVMGFO-binding sites of DDR2 and SPARC reveals a striking case of convergent evolution in collagen recognition.
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the Discoidin domain receptor ddr2 is a receptor for type x collagen
Matrix Biology, 2006Co-Authors: Birgit Leitinger, Alvin P L KwanAbstract:During endochondral ossification, collagen X is deposited in the hypertrophic zone of the growth plate. Our previous results have shown that collagen X is capable of interacting directly with chondrocytes, primarily via integrin α2β1. In this study, we determined whether collagen X could also interact with the non-integrin collagen receptors, Discoidin domain receptors (DDRs), DDR1 or DDR2. The widely expressed DDRs are receptor tyrosine kinases that are activated by a number of different collagen types. Collagen X was found to be a much better ligand for DDR2 than for DDR1. Collagen X bound to the DDR2 extracellular domain with high affinity and stimulated DDR2 autophosphorylation, the first step in transmembrane signalling. Expression of DDR2 in the epiphyseal plate was confirmed by RT-PCR and immunohistochemistry. The spatial expression of DDR2 in the hypertrophic zone of the growth plate is consistent with a physiological interaction of DDR2 with collagen X. Surprisingly, the Discoidin domain of DDR2, which fully contains the binding sites for the fibrillar collagens I and II, was not sufficient for collagen X binding. The nature of the DDR2 binding site(s) within collagen X was further analysed. In addition to a collagenous domain, collagen X contains a C-terminal NC1 domain. DDR2 was found to recognise the triple-helical region of collagen X as well as the NC1 domain. Binding to the collagenous region was dependent on the triple-helical conformation. DDR2 autophosphorylation was induced by the collagen X triple-helical region but not the NC1 domain, indicating that the triple-helical region of collagen X contains a specific DDR2 binding site that is capable of receptor activation. Our study is the first to describe a non-fibrillar collagen ligand for DDR2 and will form the basis for further studies into the biological function of collagen X during endochondral ossification.
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the d2 period of collagen ii contains a specific binding site for the human Discoidin domain receptor ddr2
Journal of Molecular Biology, 2004Co-Authors: Birgit Leitinger, Andrzej Steplewski, Andrzej FertalaAbstract:The human Discoidin domain receptors (DDRs), DDR1 and DDR2, are expressed widely and, uniquely among receptor tyrosine kinases, activated by the extracellular matrix protein collagen. This activation is due to a direct interaction of collagen with the DDR Discoidin domain. Here, we localised a specific DDR2 binding site on the triple-helical region of collagen II. Collagen II was found to be a much better ligand for DDR2 than for DDR1. As expected, DDR2 binding to collagen II was dependent on triple-helical collagen and was mediated by the DDR2 Discoidin domain. Collagen II served as a potent stimulator of DDR2 autophosphorylation, the first step in transmembrane signalling. To map the DDR2 binding site(s) on collagen II, we used recombinant collagen II variants with specific deletions of one of the four repeating D periods. We found that the D2 period of collagen II was essential for DDR2 binding and receptor autophosphorylation, whereas the D3 and D4 periods were dispensable. The DDR2 binding site on collagen II was further defined by recombinant collagen II-like proteins consisting predominantly of tandem repeats of the D2 or D4 period. The D2 construct, but not the D4 construct, mediated DDR2 binding and receptor autophosphorylation, demonstrating that the D2 period of collagen II harbours a specific DDR2 recognition site. The discovery of a site-specific interaction of DDR2 with collagen II gives novel insight into the nature of the interaction of collagen II with matrix receptors.
Robert S Molday - One of the best experts on this subject based on the ideXlab platform.
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cog wheel octameric structure of rs1 the Discoidin domain containing retinal protein associated with x linked retinoschisis
PLOS ONE, 2016Co-Authors: Martin Bush, Dheva Setiaputra, Robert S MoldayAbstract:RS1, also known as retinoschisin, is a disulphide-linked, Discoidin domain containing homo-oligomeric protein that plays a crucial role in maintaining the cellular and synaptic organization of the retina. This is highlighted by the finding that over 130 mutations in RS1 cause X-linked retinoschisis, a retinal degenerative disease characterized by the splitting of the retinal cell layers, disruption of the photoreceptor–bipolar synapses, degeneration of photoreceptors, and severe loss in central vision. In this study, we investigated the arrangement of the RS1 subunits within the oligomer complex using single particle electron microscopy. RS1 was seen as two stacked rings with each ring displaying a symmetrical cog wheel-like structure with eight teeth or projections corresponding to the RS1 subunits. Three dimensional reconstruction and molecular modelling indicated that the Discoidin domain, the principal functional unit of RS1, projects outward, and the Rs1 domain and C-terminal segment containing intermolecular disulphide bonds are present in the inner ring to form the core octameric structure. These studies provide a basis for further understanding the role of the novel core RS1 octameric complex in retinal cell biology and X-linked retinoschisis.
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retinoschisin rs1 the protein encoded by the x linked retinoschisis gene is anchored to the surface of retinal photoreceptor and bipolar cells through its interactions with a na k atpase sarm1 complex
Journal of Biological Chemistry, 2007Co-Authors: Laurie L Molday, Winco W H Wu, Robert S MoldayAbstract:Abstract Retinoschisin or RS1 is a Discoidin domain-containing protein encoded by the gene responsible for X-linked retinoschisis (XLRS), an early onset macular degeneration characterized by a splitting of the retina. Retinoschisin, expressed and secreted from photoreceptors and bipolar cells as a homo-octameric complex, associates with the surface of these cells where it serves to maintain the cellular organization of the retina and the photoreceptor-bipolar synaptic structure. To gain insight into the role of retinoschisin in retinal cell adhesion and the pathogenesis of XLRS, we have investigated membrane components in retinal extracts that interact with retinoschisin. Unlike the Discoidin domain-containing blood coagulation proteins Factor V and Factor VIII, retinoschisin did not bind to phospholipids or retinal lipids reconstituted into unilamellar vesicles or immobilized on microtiter plates. Instead, co-immunoprecipitation studies together with mass spectrometric-based proteomics and Western blotting showed that retinoschisin is associated with a complex consisting of Na/K ATPase (α3, β2 isoforms) and the sterile alpha and TIR motif-containing protein SARM1. Double labeling studies for immunofluorescence microscopy confirmed the co-localization of retinoschisin with Na/K ATPase and SARM1 in photoreceptors and bipolar cells of retina tissue. We conclude that retinoschisin binds to Na/K ATPase on photoreceptor and bipolar cells. This interaction may be part of a novel SARM1-mediated cell signaling pathway required for the maintenance of retinal cell organization and photoreceptor-bipolar synaptic structure.
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rs1 a Discoidin domain containing retinal cell adhesion protein associated with x linked retinoschisis exists as a novel disulfide linked octamer
Journal of Biological Chemistry, 2005Co-Authors: Winco W H Wu, Julie P Wong, Juergen Kast, Robert S MoldayAbstract:Abstract RS1, also known as retinoschisin, is an extracellular protein that plays a crucial role in the cellular organization of the retina. Mutations in RS1 are responsible for X-linked retinoschisis, a common, early-onset macular degeneration in males that results in a splitting of the inner layers of the retina and severe loss in vision. RS1 is assembled and secreted from photoreceptors and bipolar cells as a homo-oligomeric protein complex. Each subunit consists of a 157-amino acid Discoidin domain flanked by two small segments of 39 and 5 amino acids. To begin to understand how the structure of RS1 relates to its role in retinal cell adhesion and X-linked retinoschisis, we have determined the subunit organization and disulfide bonding pattern of RS1 by SDS gel electrophoresis, velocity sedimentation, and mass spectrometry. Our results indicate that RS1 exists as a novel octamer in which the eight subunits are joined together by Cys59-Cys223 intermolecular disulfide bonds. Subunits within the octamer are further organized into dimers mediated by Cys40-Cys40 bonds. These cysteines lie just outside the Discoidin domain indicating that these flanking segments primarily function in the octamerization of RS1. Within the Discoidin domain, two cysteine pairs (Cys63-Cys219 and Cys110-Cys142) form intramolecular disulfide bonds that are important in protein folding, and one cysteine (Cys83) exists in its reduced state. Because mutations that disrupt subunit assembly cause X-linked retinoschisis, the assembly of RS1 into a disulfide-linked homo-octamer appears to be critical for its function as a retinal cell adhesion protein.
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defective Discoidin domain structure subunit assembly and endoplasmic reticulum processing of retinoschisin are primary mechanisms responsible for x linked retinoschisis
Journal of Biological Chemistry, 2003Co-Authors: Winco W H Wu, Robert S MoldayAbstract:Abstract Retinoschisin is a 24-kDa Discoidin domain-containing protein that is secreted from photoreceptor and bipolar cells as a large disulfide-linked multisubunit complex. It functions as a cell adhesion protein to maintain the cellular organization and synaptic structure of the retina. Over 125 different mutations in the RS1 gene are associated with X-linked juvenile retinoschisis, the most common form of early onset macular degeneration in males. To identify molecular determinants important for retinoschisin structure and function and elucidate molecular and cellular mechanisms responsible for X-linked juvenile retinoschisis, we have analyzed the expression, protein folding, disulfide-linked subunit assembly, intracellular localization, and secretion of wild-type retinoschisin, 15 Cys-to-Ser variants and 12 disease-linked mutants. Our studies, together with molecular modeling of the Discoidin domain, identify Cys residues involved in intramolecular and intermolecular disulfide bonds essential for protein folding and subunit assembly. We show that misfolding of the Discoidin domain, defective disulfide-linked subunit assembly, and inability of retinoschisin to insert into the endoplasmic reticulum membrane as part of the protein secretion process are three primary mechanisms responsible for the loss in the function of retinoschisin as a cell adhesion protein and the pathogenesis of X-linked juvenile retinoschisis.
Wolfgang Vogel - One of the best experts on this subject based on the ideXlab platform.
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expression and mutation analysis of the Discoidin domain receptors 1 and 2 in non small cell lung carcinoma
British Journal of Cancer, 2007Co-Authors: Caroline E Ford, Tommy Andersson, Mingsound Tsao, Wolfgang VogelAbstract:The Discoidin domain receptors, (DDR)1 and DDR2, have been linked to numerous human cancers. We sought to determine expression levels of DDRs in human lung cancer, investigate prognostic determinates, and determine the prevalence of recently reported mutations in these receptor tyrosine kinases. Tumour samples from 146 non-small cell lung carcinoma (NSCLC) patients were analysed for relative expression of DDR1 and DDR2 using quantitative real-time PCR (qRT-PCR). An additional 23 matched tumour and normal tissues were tested for differential expression of DDR1 and DDR2, and previously reported somatic mutations. Discoidin domain receptor 1 was found to be significantly upregulated by 2.15-fold (P=0.0005) and DDR2 significantly downregulated to an equivalent extent (P=0.0001) in tumour vs normal lung tissue. Discoidin domain receptor 2 expression was not predictive for patient survival; however, DDR1 expression was significantly associated with overall (hazard ratio (HR) 0.43, 95% CI=0.22–0.83, P=0.014) and disease-free survival (HR=0.56, 95% CI=0.33–0.94, P=0.029). Multivariate analysis revealed DDR1 is an independent favourable predictor for prognosis independent of tumour differentiation, stage, histology, and patient age. However, contrary to previous work, we did not observe DDR mutations. We conclude that whereas altered expression of DDRs may contribute to malignant progression of NSCLC, it is unlikely that this results from mutations in the DDR1 and DDR2 genes that we investigated.
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sensing extracellular matrix an update on Discoidin domain receptor function
Cellular Signalling, 2006Co-Authors: Wolfgang Vogel, Rahim Abdulhussein, Caroline E FordAbstract:Discoidin Domain Receptors (DDRs) have recently emerged as non-integrin-type receptors for collagen. The two mammalian gene products Discoidin Domain Receptor 1 and -2 constitute a subfamily of tyrosine kinase receptors that are selectively expressed in a number of different cell types and organs. Upon collagen activation, DDRs regulate cell adhesion, proliferation and extracellular matrix remodeling. Here we review the various signaling pathways and cellular responses evoked by activated DDRs. Additionally, we give an overview of the more recent advances in understanding the role of DDRs in various human diseases, in particular during tumor progression, atherosclerosis, inflammation and tissue fibrosis. Furthermore, we discuss potential roles of genes homologous to mammalian DDRs identified in flies, worms and sponges. We show that the structural organization of these DDR-related genes is highly conserved throughout evolution suggesting that invertebrate DDRs may also function as receptors for collagen. By highlighting current questions about these unusual collagen receptors, we hope to attract new research on DDRs from a variety of different fields.
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Expression of Discoidin domain receptor 1 during mouse brain development follows the progress of myelination.
Neuroscience, 2006Co-Authors: Neus Franco-pons, C. Virgos, Wolfgang Vogel, Jesús M. Ureña, Eduardo Soriano, Elisabet VilellaAbstract:Discoidin domain receptor 1 is a tyrosine kinase receptor expressed in a variety of tissues including the brain. This study describes mRNA and protein expression of Discoidin domain receptor 1 in mouse brain during development and provides new insights into its role during gliogenesis and neurogenesis. We performed in situ hybridization for Discoidin domain receptor 1 in mouse brains at embryonic day 18, postnatal days 5, 9, 15, 21 and adulthood and observed a diffuse pattern in the proliferative areas during embryogenesis. From postnatal day 5 onwards, a defined cellular expression pattern of Discoidin domain receptor 1 was observed, mainly located in white matter tracts and following a spatio-temporal pattern that overlapped the progress of myelination. Next, we performed double-labeling reactions (in situ hybridization followed by immunohistochemistry) that confirmed that Discoidin domain receptor 1 was expressed by mature oligodendrocytes. We observed that cells positive for Discoidin domain receptor 1 also expressed carnosine and anti-adenomatous polyposis coli, two mature oligodendrocyte markers. Based on the localization of Discoidin domain receptor 1 specifically in the white matter fiber tracts during postnatal development, we suggest that Discoidin domain receptor 1 participates in the development and maintenance of the myelin sheath.
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expression and signaling activity of wnt 5a Discoidin domain receptor 1 and syk plays distinct but decisive roles in breast cancer patient survival
Clinical Cancer Research, 2005Co-Authors: Janna Dejmek, Wolfgang Vogel, Karin Leandersson, Jonas Manjer, Anders Bjartell, Stefan O Emdin, Goran Landberg, Tommy AnderssonAbstract:Expression and signaling activity of Wnt-5a/Discoidin domain receptor-1 and Syk plays distinct but decisive roles in breast cancer patient survival.
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tyrosine kinase activity of Discoidin domain receptor 1 is necessary for smooth muscle cell migration and matrix metalloproteinase expression
Circulation Research, 2002Co-Authors: Wolfgang Vogel, Michelle P BendeckAbstract:Smooth muscle cell (SMC) interactions with collagen mediate cell migration during the pathogenesis of atherosclerosis and restenosis. Discoidin domain receptors (DDRs) have been identified as novel collagen receptors. We used aortic SMCs from wild-type and DDR1−/− mice to evaluate the function of the DDR1 in regulating migration. DDR1−/− SMCs exhibited impaired attachment to and migration toward a type I collagen substrate. Matrix metalloproteinase-2 (MMP-2) and MMP-9 activities were concomitantly reduced in these cells. Transfection of a full-length cDNA for DDR1b rescued these deficits, whereas kinase-dead mutants of DDR1 restored attachment but not migration and MMP production. These results suggest that active DDR1 kinase is a central mediator of SMC migration.
Erhard Hohenester - One of the best experts on this subject based on the ideXlab platform.
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collagen recognition and transmembrane signalling by Discoidin domain receptors
Biochimica et Biophysica Acta, 2013Co-Authors: Federico Carafoli, Erhard HohenesterAbstract:The Discoidin domain receptors, DDR1 and DDR2, are two closely related receptor tyrosine kinases that are activated by triple-helical collagen in a slow and sustained manner. The DDRs have important roles in embryo development and their dysregulation is associated with human diseases, such as fibrosis, arthritis and cancer. The extracellular region of DDRs consists of a collagen-binding Discoidin (DS) domain and a DS-like domain. The transmembrane region mediates the ligand-independent dimerisation of DDRs and is connected to the tyrosine kinase domain by an unusually long juxtamembrane domain. The major DDR binding site in fibrillar collagens is a GVMGFO motif (O is hydroxyproline), which is recognised by an amphiphilic trench at the top of the DS domain. How collagen binding leads to DDR activation is not understood. GVMGFO-containing triple-helical peptides activate DDRs with the characteristic slow kinetics, suggesting that the supramolecular structure of collagen is not required. Activation can be blocked allosterically by monoclonal antibodies that bind to the DS-like domain. Thus, collagen most likely causes a conformational change within the DDR dimer, which may lead to the formation of larger DDR clusters. This article is part of a Special Issue entitled: Emerging recognition and activation mechanisms of receptor tyrosine kinases.
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structure of the Discoidin domain receptor 1 extracellular region bound to an inhibitory fab fragment reveals features important for signaling
Structure, 2012Co-Authors: Federico Carafoli, Birgit Leitinger, Marie Cathrin Mayer, Kazushige Shiraishi, Mira Anguelova Pecheva, Lai Yi Chan, Erhard HohenesterAbstract:The Discoidin domain receptors, DDR1 and DDR2, are constitutively dimeric receptor tyrosine kinases that are activated by triple-helical collagen. Aberrant DDR signaling contributes to several human pathologies, including many cancers. We have generated monoclonal antibodies (mAbs) that inhibit DDR1 signaling without interfering with collagen binding. The crystal structure of the monomeric DDR1 extracellular region bound to the Fab fragment of mAb 3E3 reveals that the collagen-binding Discoidin (DS) domain is tightly associated with the following DS-like domain, which contains the epitopes of all mAbs. A conserved surface patch in the DS domain outside the collagen-binding site is shown to be required for signaling. Thus, the active conformation of the DDR1 dimer involves collagen-induced contacts between the DS domains, in addition to the previously identified association of transmembrane helices. The mAbs likely inhibit signaling by sterically blocking the extracellular association of DDR1 subunits.
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crystallographic insight into collagen recognition by Discoidin domain receptor 2
Structure, 2009Co-Authors: Federico Carafoli, Birgit Leitinger, Dominique Bihan, Stavros Stathopoulos, Antonios D Konitsiotis, Marc Kvansakul, Richard W Farndale, Erhard HohenesterAbstract:The Discoidin domain receptors, DDR1 and DDR2, are widely expressed receptor tyrosine kinases that are activated by triple-helical collagen. They control important aspects of cell behavior and are dysregulated in several human diseases. The major DDR2-binding site in collagens I–III is a GVMGFO motif (O is hydroxyproline) that also binds the matricellular protein SPARC. We have determined the crystal structure of the Discoidin domain of human DDR2 bound to a triple-helical collagen peptide. The GVMGFO motifs of two collagen chains are recognized by an amphiphilic pocket delimited by a functionally critical tryptophan residue and a buried salt bridge. Collagen binding results in structural changes of DDR2 surface loops that may be linked to the process of receptor activation. A comparison of the GVMGFO-binding sites of DDR2 and SPARC reveals a striking case of convergent evolution in collagen recognition.
Annabelle Varrot - One of the best experts on this subject based on the ideXlab platform.
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Discoidin i from dictyostelium discoideum and interactions with oligosaccharides specificity affinity crystal structures and comparison with Discoidin ii
Journal of Molecular Biology, 2010Co-Authors: Sophie Mathieu, K.s. Aragao, Anne Imberty, Annabelle VarrotAbstract:Abstract Discoidin I (DiscI) and Discoidin II (DiscII) are N -acetylgalactosamine (GalNAc)-binding proteins from Dictyostelium discoideum . They consist of two domains: an N-terminal Discoidin domain and a C-terminal H-type lectin domain. They were cloned and expressed in high yield in recombinant form in Escherichia coli . Although both lectins bind galactose (Gal) and GalNAc, glycan array experiments performed on the recombinant proteins displayed strong differences in their specificity for oligosaccharides. DiscI and DiscII bind preferentially to Gal/GalNAcβ1–3Gal/GalNAc-containing and Gal/GalNAcβ1–4GlcNAcβ1–6Gal/GalNAc-containing glycans, respectively. The affinity of the interaction of DiscI with monosaccharides and disaccharides was evaluated using isothermal titration calorimetry experiments. The three-dimensional structures of native DiscI and its complexes with GalNAc, GalNAcβ1–3Gal, and Galβ1–3GalNAc were solved by X-ray crystallography. DiscI forms trimers with involvement of calcium at the monomer interface. The N-terminal Discoidin domain presents a structural similarity to F-type lectins such as the eel agglutinin, where an amphiphilic binding pocket suggests possible carbohydrate-binding activity. In the C-terminal H-type lectin domain, the GalNAc residue establishes specific hydrogen bonds that explain the observed affinity ( K d = 3 × 10 − 4 M). The different specificities of DiscI and DiscII for oligosaccharides were rationalized from the different structures obtained by either X-ray crystallography or molecular modeling.
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Structure determination of Discoidin II from Dictyostelium discoideum and carbohydrate binding properties of the lectin domain.
Proteins, 2008Co-Authors: K.s. Aragao, Michel Satre, Anne Imberty, Annabelle VarrotAbstract:The social amoeba Dictyostelium discoideum adopts a cohesive stage upon starvation and then produces Discoidin I and II, two proteins able to bind galactose and N-acetyl-galactosamine. The N-terminal domain or Discoidin domain (DS) is widely distributed in eukaryotes where it plays a role in extracellular matrix binding while the C-terminal domain displays sequence similarities to invertebrate lectins. We present the first X-ray structures of the wild-type and recombinant Discoidin II in unliganded state and in complex with monosaccharides. The protein forms a homotrimer which presents two binding surfaces situated on the opposite boundaries of the structure. The binding sites of the N-terminal domain contain PEG molecules that could mimics binding of natural ligand. The C-terminal lectin domain interactions with N-acetyl-D-galactosamine and methyl-beta-galactoside are described. The carbohydrate binding sites are located at the interface between monomers. Specificity for galacto configuration can be rationalized since the axial O4 hydroxyl group is involved in several hydrogen bonds with protein side chains. Titration microcalorimetry allowed characterization of affinity and demonstrated the enthalpy-driven character of the interaction. Those results highlight the structural differentiation of the DS domain involved in many cell-adhesion processes from the lectin activity of Dictyostelium Discoidins.