title: Functional significance of conserved glycine 127 in a human dual-specificity protein tyrosine phosphatase.
abstract: Using site-directed mutagenesis and steady-state kinetic measurements, the functional role of the conserved glycine 127 in a human vaccinia H1-related phosphatase (VHR) was investigated. The mutations of Gly127 to Ala and Pro resulted in a significant decrease in k(cat)/K(m), and increase in K(i) for arsenate, indicating that flexibility at the Gly127 site has a large effect on substrate binding and catalytic activity. No substantial decrease in k(cat)/K(m) and increase in K(i) values were observed for G127 deletion mutant. This showed the conformational flexibility of the PTP loop also affected the enzymatic activity of VHR. Our data suggest that the flexibility of the PTP loop in VHR is probably controlled by Gly127, and that even subtle changes in the loop flexibility may interfere with substrate binding and enzymatic reaction.
authors.affiliation: Key Laboratory of Structural Biology, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, China.
authors.forename: W-Y
authors.initials: WY
authors.lastname: Zeng
authors.forename: Y-H
authors.initials: YH
authors.lastname: Wang
authors.forename: Y-C
authors.initials: YC
authors.lastname: Zhang
authors.forename: W-L
authors.initials: WL
authors.lastname: Yang
authors.forename: Y-Y
authors.initials: YY
authors.lastname: Shi
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001149:Arsenates / Q000378:metabolism / Q000494:pharmacology; D001665:Binding Sites; D002942:Circular Dichroism; D017124:Conserved Sequence; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D005998:Glycine / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D013379:Substrate Specificity
chemical_list: D001149:Arsenates; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D017027:Protein Tyrosine Phosphatases; C025657:arsenic acid; D005998:Glycine