Effect of ionic strength and oxidation on the P-loop conformation of the protein tyrosine phosphatase-like phytase, PhyAsr.
نویسندگان
چکیده
The protein tyrosine phosphatase (PTP)-like phytase, PhyAsr, from Selenomonas ruminantium is a novel member of the PTP superfamily, and the only described member that hydrolyzes myo-inositol-1,2,3,4,5,6-hexakisphosphate. In addition to the unique substrate specificity of PhyAsr, the phosphate-binding loop (P-loop) has been reported to undergo a conformational change from an open (inactive) to a closed (active) conformation upon ligand binding at low ionic strength. At high ionic strengths, the P-loop was observed in the closed, active conformation in both the presence and absence of ligand. To test whether the P-loop movement can be induced by changes in ionic strength, we examined the effect that ionic strength has on the catalytic efficiency of PhyAsr, and determined the structure of the enzyme at several ionic strengths. The catalytic efficiency of PhyAsr is highly sensitive to ionic strength, with a seven-fold increase in k(cat)/K(m) and a ninefold decrease in K(m) when the ionic strength is increased from 100 to 500 mm. Surprisingly, the P-loop is observed in the catalytically competent conformation at all ionic strengths, despite the absence of a ligand. Here we provide structural evidence that the ionic strength dependence of PhyAsr and the conformational change in the P-loop are not linked. Furthermore, we demonstrate that the previously reported P-loop conformational change is a result of irreversible oxidation of the active site thiolate. Finally, we rationalize the observed P-loop conformational changes observed in all oxidized PTP structures.
منابع مشابه
Kinetic and structural analysis of a bacterial protein tyrosine phosphatase-like myo-inositol polyphosphatase.
PhyA from Selenomonas ruminantium (PhyAsr), is a bacterial protein tyrosine phosphatase (PTP)-like inositol polyphosphate phosphatase (IPPase) that is distantly related to known PTPs. PhyAsr has a second substrate binding site referred to as a standby site and the P-loop (HCX5R) has been observed in both open (inactive) and closed (active) conformations. Site-directed mutagenesis and kinetic an...
متن کاملEffect of dietary zinc oxide and phytase on the plasma metabolites and enzyme activities in aged broiler breeder hens
Background: It has been shown that zinc has an effect on physiological responses in animals and birds. On the other hand, dietary phytase in poultry results in increased availability of zinc. OBJECTIVES: This study was conducted to investigate the effects of zinc oxide (ZnO) and Escherichia coli-derived 6-phytase supplemented diets on the plasma metabolites and enzyme activities of broiler bree...
متن کاملSodium Orthovanadate Treatment Reverses Protracted Methionine Administration Induced Schizophrenia Like Behavior in Rats
Suppression of Akt (Protein kinase B) has been implicated in schizophrenia, the effect which has been documented to be reversed by tyrosine phosphatase inhibition. T hus, present study has been designed to study the effect of sodium orthovanadate, a tyrosine phosphatase inhibitor, on protracted methionine administration induced schizophrenia like behavior in rats. Schizophrenia...
متن کاملبررسی تاثیر آسکوربیک اسید بر واکنش گلیکاسیون آلبومین در شرایط برونتنی
Background & Aims: Advanced glycation end products (AGEs) formation is increased in diabetes mellitus, leading to microvascular and macrovascular complications. Recently, much attention has been focused on natural and synthetic inhibitors to delay the onset or progression of diabetes and its comorbidities. In this study, an in vitro glycation model containing albumin as a model protein together...
متن کاملRegional Assignment of Ptpre Encoding Protein Tyrosine Phosphataes ε to Mouse Chromosome 7F3
Protein tyrosine phosphatases (PTPases) regulate the tyrosine phosphorylation of target proteins involved in several biological activities including cell proliferation and transformation. Protein tyrosine phosphatase E (PTPE) contains duplicated PTPase-like domains and a short extracellular region. Using the fluorescence in situ hybridization method, the gene encoding PTPE (locus symbol Ptpre...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- The FEBS journal
دوره 275 15 شماره
صفحات -
تاریخ انتشار 2008