2aut
From Proteopedia
Crystal structure of Lys154Asn mutant of mature AphA of S. typhimurium
Structural highlights
Function[APHA_SALTY] Dephosphorylates several organic phosphate monoesters such as 3'-UMP, 5'-UMP and pNPP. Also has a phosphotransferase activity catalyzing the transfer of low-energy phosphate groups from organic phosphate monoesters to free hydroxyl groups of various organic compounds such as the 2'-, 3-, or 5'-hydroxyls of nucleosides and nucleotides. Also displays significant phosphomutase activity since it is able to catalyze the transfer of the phosphate group of 3'-AMP from the 3'-position both to the 2'- and 5'-positions. One of the physiological functions of the phosphohydrolytic activity of the enzyme is believed to be the scavenging of organic phosphate esters that otherwise cannot pass the cytoplasmic membrane.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe Salmonella typhimurium class B nonspecific acid phosphatase (AphA protein) belongs to the L2-haloacid dehalogenase superfamily. The conserved Lys-154 interacts with substrate phosphate, nucleophile Asp-46, and Asp-173 in the wild-type AphA protein. Asp-173 also interacts with Mg(II) water ligand and with main-chain amide of loop-4. We report here the mutational analysis of Lys-154 and Asp-173, the crystal structures of the K154N and K154R mutants, and the results of electrostatic potential calculations. The K154N, K154R and D173N mutants display significant reduction in the phosphatase activity. Lys-154 may not be responsible for a juxtaposition of the substrate phosphate and the aspartyl nucleophile, but has an hitherto unknown functional role of rendering the substrate phosphorous atom electron deficient. Nearly 10,000-fold increase in the K(d) value for dissociation of the cofactor Mg(II) observed for the D173N mutant correlates well with theoretically estimated change in the binding free energy of Mg(II). Structural and mutational analyses reveal the functional role of active-site Lys-154 and Asp-173 of Salmonella typhimurium AphA protein.,Makde RD, Gupta GD, Mahajan SK, Kumar V Arch Biochem Biophys. 2007 Aug 1;464(1):70-9. Epub 2007 May 30. PMID:17570338[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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