The Experts below are selected from a list of 6978 Experts worldwide ranked by ideXlab platform
Ronald H Kaback - One of the best experts on this subject based on the ideXlab platform.
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site directed alkylation of lacy effect of the proton electrochemical gradient
Journal of Molecular Biology, 2007Co-Authors: Natalia Ermolova, Ronald H KabackAbstract:Previous N-ethylmaleimide-labeling studies show that ligand binding increases the reactivity of single-Cys mutants located predominantly on the periplasmic side of LacY and decreases reactivity of mutants located for the most part on the cytoplasmic side. Thus, sugar binding appears to induce opening of a periplasmic pathway with closing of the cytoplasmic cavity resulting in alternative access of the sugar-binding site to either side of the membrane. Here we describe the use of a fluorescent alkylating reagent that reproduces the previous observations with respect to sugar binding. We then show that generation of an H + electrochemical gradient ( Δμ + , interior negative) increases the reactivity of single-Cys mutants on the periplasmic side of the sugar-binding site and in the putative hydrophilic pathway. The results suggest that Δμ + , like sugar, acts to increase the probability of opening on the periplasmic side of LacY.
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binding affinity of lactose permease is not altered by the h electrochemical gradient
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Lan Guan, Ronald H KabackAbstract:Abstract The x-ray structure of lactose permease of Escherichia coli (LacY) exhibits a single sugar-binding site at the apex of a hydrophilic cavity open to the cytoplasm, and it has been postulated that the binding site has alternating access to either side of the membrane during turnover. Here, the affinity of LacY for ligand in right-side-out or inside-out membrane vesicles is measured in the absence or presence of an H+ electrochemical gradient () by utilizing ligand protection against alkylation. Right-side-out or inside-out membrane vesicles containing LacY with a single cysteine residue at position 148 exhibit K D values for lactose or β-d-galactopyranosyl 1-thio-β-d-galactopyranoside of ≈1.0 mM or 40 μM, respectively, and no systematic change is observed in the presence of under conditions in which there is little or no accumulation of ligand. The results are consistent with a mechanism in which the major effect of on sugar accumulation is caused by an increased rate of deprotonation on the inner face of the membrane, leading to an increase in the rate of return of the unloaded symporter to the outer face of the membrane. membranes bioenergetics transport H+ symport membrane protein structure
Christopher John Schofield - One of the best experts on this subject based on the ideXlab platform.
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Crystal Structure and Mechanistic Implications of 1-Aminocyclopropane-1-Carboxylic Acid Oxidase—The Ethylene-Forming Enzyme
Chemistry & Biology, 2004Co-Authors: Zhihong Zhang, Jing-shang Ren, I J Clifton, Christopher John SchofieldAbstract:The final step in the biosynthesis of the plant signaling molecule ethylene is catalyzed by 1-aminocyclopro- pane-1-carboxylic acid oxidase (ACCO). ACCO re- quires bicarbonate as an activator and catalyzes the oxidation of ACC to give ethylene, CO2, and HCN. We report crystal structures of ACCO in apo-form (2.1 A˚ resolution) and complexed with Fe(II) (2.55 A˚ ) or Co(II) (2.4 A˚ ). The active site contains a single Fe(II) ligated by three residues (His177, Asp179, and His234), and it is relatively open compared to those of the 2-oxoglu- tarate oxygenases. The side chains of Arg175 and Arg244, proposed to be involved in binding bicarbon- ate, project away from the active site, but conforma- tional changes may allow either or both to enter the active site. The structures will form a basis for future mechanistic and inhibition studies.
Anthony R. Mundy - One of the best experts on this subject based on the ideXlab platform.
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the morbidity of buccal mucosal graft harvest for urethroplasty and the effect of nonclosure of the graft harvest site on postoperative pain
The Journal of Urology, 2004Co-Authors: Dan Wood, S E Allen, Tamsin Greenwell, Daniela E Andrich, Anthony R. MundyAbstract:ABSTRACT Purpose: We assess the medium and long-term morbidity of buccal mucosal graft (BMG) harvest for urethroplasty, and evaluate the effect of nonclosure of the graft harvest site on postoperative pain. Materials and Methods: A questionnaire was mailed to 110 men who underwent BMG urethroplasty between January 1, 1997 and August 31, 2002. Demographic data and side effects of BMG harvest, including oral pain, sensation and intake, were assessed postoperatively. A prospective study was then performed to compare 20 unselected men whose BMG donor site was closed with a group of 20 men in whom it was left open using a 5-point analog pain score that was completed twice daily for the first 5 postoperative days. Results: A total of 49 men with a median age of 49 years (range 23 to 73) returned questionnaires relating to 57 BMG harvests. Of the graft harvests 47 (83%) were associated with postoperative pain, which was worse than expected in 24 (51%). Of the 57 patients 51 (90%) resumed oral liquid intake within 24 hours and 44 (77%) resumed normal diet within 1 week. Postoperative side effects included perioral numbness in 39 (68%) patients with 15 (26%) having residual numbness after 6 months, initial difficulty with mouth opening in 38 (67%) with 5 (9%) having persistent problems, changes in salivation in 6 (11%) and mucous retention cyst that required excision in 1 (2%). The men in the prospective donor site study had a median age of 51 years (range 24 to 70). Mean pain score for patients with donor site closure was 3.68 and was significantly higher than that for patients without donor site closure (2.26, p Conclusions: Buccal mucosal graft harvest is not a pain-free procedure. Closure of the harvest donor site appears to worsen this pain and it may be best to leave harvest sites open. The main long-term complications are perioral numbness, persistent difficulty with mouth opening and change in salivary function.
Zhihong Zhang - One of the best experts on this subject based on the ideXlab platform.
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Crystal Structure and Mechanistic Implications of 1-Aminocyclopropane-1-Carboxylic Acid Oxidase—The Ethylene-Forming Enzyme
Chemistry & Biology, 2004Co-Authors: Zhihong Zhang, Jing-shang Ren, I J Clifton, Christopher John SchofieldAbstract:The final step in the biosynthesis of the plant signaling molecule ethylene is catalyzed by 1-aminocyclopro- pane-1-carboxylic acid oxidase (ACCO). ACCO re- quires bicarbonate as an activator and catalyzes the oxidation of ACC to give ethylene, CO2, and HCN. We report crystal structures of ACCO in apo-form (2.1 A˚ resolution) and complexed with Fe(II) (2.55 A˚ ) or Co(II) (2.4 A˚ ). The active site contains a single Fe(II) ligated by three residues (His177, Asp179, and His234), and it is relatively open compared to those of the 2-oxoglu- tarate oxygenases. The side chains of Arg175 and Arg244, proposed to be involved in binding bicarbon- ate, project away from the active site, but conforma- tional changes may allow either or both to enter the active site. The structures will form a basis for future mechanistic and inhibition studies.
Junji Iwahara - One of the best experts on this subject based on the ideXlab platform.
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A chemical approach for site-specific identification of NMR signals from protein side-chain NH_3 ^+ groups forming intermolecular ion pairs in protein–nucleic acid complexes
Journal of Biomolecular NMR, 2015Co-Authors: Kurtis M. Anderson, Dan Nguyen, Alexandre Esadze, Levani Zandrashvili, David G. Gorenstein, Junji IwaharaAbstract:Protein–nucleic acid interactions involve intermolecular ion pairs of protein side-chain and DNA or RNA phosphate groups. Using three protein–DNA complexes, we demonstrate that site-specific oxygen-to-sulfur substitution in phosphate groups allows for identification of NMR signals from the protein side-chain NH_3 ^+ groups forming the intermolecular ion pairs. A characteristic change in their ^1H and ^15N resonances upon this modification (i.e., substitution of phosphate to phosphorodithioate) can represent a signature of an intermolecular ion pair. Hydrogen-bond scalar coupling between protein side-chain ^15N and DNA phosphorodithiaote ^31P nuclei provides direct confirmation of the intermolecular ion pair. The same approach is likely applicable to protein–RNA complexes as well.
