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Alanine

The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform

James R. Knox – 1st expert on this subject based on the ideXlab platform

  • Enzymes of vancomycin resistance: The structure of D-Alanine-D-lactate ligase of naturally resistant Leuconostoc mesenteroides
    Structure, 2000
    Co-Authors: Alexandre P. Kuzin, Tao Sun, Jodi Jorczak-baillass, Vicki L. Healy, Christopher T. Walsh, James R. Knox

    Abstract:

    Background: The bacterial cell wall and the enzymes that synthesize it are targets of glycopeptide antibiotics (vancomycins and teicoplanins) and β-lactams (penicillins and cephalosporins). Biosynthesis of cell wall peptidoglycan requires a crosslinking of peptidyl moieties on adjacent glycan strands. The D-Alanine-D-Alanine transpeptidase, which catalyzes this crosslinking, is the target of β-lactam antibiotics. Glycopeptides, in contrast, do not inhibit an enzyme, but bind directly to D-Alanine-D-Alanine and prevent subsequent crosslinking by the transpeptidase. Clinical resistance to vancomycin in enterococcal pathogens has been traced to altered ligases producing D-Alanine-D-lactate rather than D-Alanine-D-Alanine. Results: The structure of a D-Alanine-D-lactate ligase has been determined by multiple anomalous dispersion (MAD) phasing to 2.4 Å resolution. Co- crystallization of the Leuconostoc mesenteroides LmDdl2 ligase with ATP and a di-D-methylphosphinate produced ADP and a phosphinophosphate analog of the reaction intermediate of cell wall peptidoglycan biosynthesis. Comparison of this D-Alanine-D-lactate ligase with the known structure of DdlB D-Alanine-D- Alanine ligase, a wild-type enzyme that does not provide vancomycin resistance, reveals alterations in the size and hydrophobicity of the site for D-lactate binding (subsite 2). A decrease was noted in the ability of the ligase to hydrogen bond a substrate molecule entering subsite 2. Conclusions: Structural differences at subsite 2 of the D-Alanine-D-lactate ligase help explain a substrate specificity shift (D-Alanine to D-lactate) leading to remodeled cell wall peptidoglycan and vancomycin resistance in Gram-positive pathogens.

Jean-michel Masson – 2nd expert on this subject based on the ideXlab platform

  • Alanine-stretch scanning mutagenesis: a simple and efficient method to probe protein structure and function
    Nucleic Acids Research, 1997
    Co-Authors: Fabrice Lefevre, Marie Hélène Rémy, Jean-michel Masson

    Abstract:

    We have developed a foolproof method to substitute a stretch of residues by Alanines. After the introduction of a PstI site by IPCR, thus creating two Alanine codons, additional codons are introduced at this site through the use of an ‘Alanine-stretch cartridge’. These cartridges comprise an antibiotic resistance gene flanked on both sides by Alanine codons. Excision of the resistance gene by PvuII then yields the correct insertion of codons. The method is both highly reliable and flexible and should be of general use.

Alexandre P. Kuzin – 3rd expert on this subject based on the ideXlab platform

  • Enzymes of vancomycin resistance: The structure of D-Alanine-D-lactate ligase of naturally resistant Leuconostoc mesenteroides
    Structure, 2000
    Co-Authors: Alexandre P. Kuzin, Tao Sun, Jodi Jorczak-baillass, Vicki L. Healy, Christopher T. Walsh, James R. Knox

    Abstract:

    Background: The bacterial cell wall and the enzymes that synthesize it are targets of glycopeptide antibiotics (vancomycins and teicoplanins) and β-lactams (penicillins and cephalosporins). Biosynthesis of cell wall peptidoglycan requires a crosslinking of peptidyl moieties on adjacent glycan strands. The D-Alanine-D-Alanine transpeptidase, which catalyzes this crosslinking, is the target of β-lactam antibiotics. Glycopeptides, in contrast, do not inhibit an enzyme, but bind directly to D-Alanine-D-Alanine and prevent subsequent crosslinking by the transpeptidase. Clinical resistance to vancomycin in enterococcal pathogens has been traced to altered ligases producing D-Alanine-D-lactate rather than D-Alanine-D-Alanine. Results: The structure of a D-Alanine-D-lactate ligase has been determined by multiple anomalous dispersion (MAD) phasing to 2.4 Å resolution. Co- crystallization of the Leuconostoc mesenteroides LmDdl2 ligase with ATP and a di-D-methylphosphinate produced ADP and a phosphinophosphate analog of the reaction intermediate of cell wall peptidoglycan biosynthesis. Comparison of this D-Alanine-D-lactate ligase with the known structure of DdlB D-Alanine-D- Alanine ligase, a wild-type enzyme that does not provide vancomycin resistance, reveals alterations in the size and hydrophobicity of the site for D-lactate binding (subsite 2). A decrease was noted in the ability of the ligase to hydrogen bond a substrate molecule entering subsite 2. Conclusions: Structural differences at subsite 2 of the D-Alanine-D-lactate ligase help explain a substrate specificity shift (D-Alanine to D-lactate) leading to remodeled cell wall peptidoglycan and vancomycin resistance in Gram-positive pathogens.