Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The large HAD (haloacid dehalogenase) superfamily of hydrolases comprises P-type ATPases, phosphatases, epoxide hydrolases and L-2-haloacid dehalogenases. A comparison of the three-dimensional structure of L-2-haloacid dehalogenase with that of the response regulator protein CheY allowed the assignment of a conserved pair of aspartate residues as the Mg2+-binding site in the P-type ATPase and phosphatase members of the superfamily. From the resulting model of the active site, a conserved serine/threonine residue is suggested to be involved in phosphate binding, and a mechanism comprising a phosphoaspartate intermediate is postulated.
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PMID:Identification of the Mg2+-binding site in the P-type ATPase and phosphatase members of the HAD (haloacid dehalogenase) superfamily by structural similarity to the response regulator protein CheY. 1019 Dec 50

The crystal structure of the YrbI protein from Haemophilus influenzae (HI1679) was determined at a 1.67-A resolution. The function of the protein had not been assigned previously, and it is annotated as hypothetical in sequence databases. The protein exhibits the alpha/beta-hydrolase fold (also termed the Rossmann fold) and resembles most closely the fold of the L-2-haloacid dehalogenase (HAD) superfamily. Following this observation, a detailed sequence analysis revealed remote homology to two members of the HAD superfamily, the P-domain of Ca(2+) ATPase and phosphoserine phosphatase. The 19-kDa chains of HI1679 form a tetramer both in solution and in the crystalline form. The four monomers are arranged in a ring such that four beta-hairpin loops, each inserted after the first beta-strand of the core alpha/beta-fold, form an eight-stranded barrel at the center of the assembly. Four active sites are located at the subunit interfaces. Each active site is occupied by a cobalt ion, a metal used for crystallization. The cobalt is octahedrally coordinated to two aspartate side-chains, a backbone oxygen, and three solvent molecules, indicating that the physiological metal may be magnesium. HI1679 hydrolyzes a number of phosphates, including 6-phosphogluconate and phosphotyrosine, suggesting that it functions as a phosphatase in vivo. The physiological substrate is yet to be identified; however the location of the gene on the yrb operon suggests involvement in sugar metabolism.
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PMID:From structure to function: YrbI from Haemophilus influenzae (HI1679) is a phosphatase. 1183 14

P-type ATPases such as the sodium pump appear to be members of a superfamily of hydrolases structurally typified by the L-2-haloacid dehalogenases. In the dehalogenase L-DEX-ps, Lys151 serves to stabilize the excess negative charge in the substrate/reaction intermediates and Asp180 coordinates a water molecule that is directly involved in ester intermediate hydrolysis. To investigate the importance of the corresponding Lys691 and Asp714 of the sodium pump alpha subunit, sodium pump mutants were expressed in yeast and analyzed for their properties. Lys691Ala, Lys691Asp, Asp714Ala, and Asp714Arg mutants were inactive, not only with respect to ATPase activity but also to interaction with the highly sodium pump-specific inhibitors ouabain or palytoxin (PTX). In contrast, conservative mutants Lys691Arg and Asp714Glu retained some of the partial activities of the wild-type enzyme, although they completely failed to display any ATPase activity. Yeast cells expressing Lys691Arg and Asp714Glu mutants are sensitive to the sodium pump-specific inhibitor PTX and lose intracellular K+. Their sensitivity to PTX, with EC50 values of 118 +/- 24 and 76.5 +/- 3.6 nM, respectively, was clearly reduced by almost 7- or 4-fold below that of the native sodium pump (17.8 +/- 2.7 nM). Ouabain was recognized under these conditions with low affinity by the mutants and inhibited the PTX-induced K+ efflux from the yeast cells. The EC50 for the ouabain effect was 183 +/- 20 microM for Lys691Arg and 2.3 +/- 0.08 mM for the Asp714Glu mutant. The corresponding value obtained with cells expressing the native sodium pump was 69 +/- 18 microM. In the presence of Pi and Mg2+, none of the mutant sodium pumps were able to bind ouabain. When Mg2+ was omitted, however, both Lys691Asp and Asp714Glu mutants displayed ouabain binding that was reduced by Mg2+ with an EC50 of 0.76 +/- 0.11 and 2.3 +/- 0.2 mM, respectively. In the absence of Mg2+, ouabain binding was also reduced by K+. The EC50 values were 1.33 +/- 0.23 mM for the wild-type enzyme, 0.93 +/- 0.2 mM for the Lys691Arg mutant, and 1.02 +/- 0.24 mM for the Asp714Glu enzyme. None of the neutral or nonconservative mutants displayed any ouabain-sensitive ATPase activity. Ouabain-sensitive phosphatase activity, however, was present in membranes containing either the wild-type (1105 +/- 100 micromol of p-nitrophenol phosphate hydrolyzed min(-1) mg of protein(-1)) or the Asp714Glu mutant (575 +/- 75 micromol min(-1) mg(-1)) sodium pump. Some phosphatase activity was also associated with the Lys691Arg mutant (195 +/- 63 micromol min(-1) mg(-1)). The results are consistent with Lys691 and Asp714 being essential for the phosphorylation/dephosphorylation process that allows the sodium pump to accomplish the catalytic cycle.
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PMID:Lys691 and Asp714 of the Na+/K+-ATPase alpha subunit are essential for phosphorylation, dephosphorylation, and enzyme turnover. 1509 42