1psc
From Proteopedia
PHOSPHOTRIESTERASE FROM PSEUDOMONAS DIMINUTA
Structural highlights
Function[OPD_BREDI] Has an unusual substrate specificity for synthetic organophosphate triesters and phosphorofluoridates. All of the phosphate triesters found to be substrates are synthetic compounds. The identity of any naturally occurring substrate for the enzyme is unknown. Has no detectable activity with phosphate monoesters or diesters and no activity as an esterase or protease. It catalyzes the hydrolysis of the insecticide paraoxon at a rate approaching the diffusion limit and thus appears to be optimally evolved for utilizing this synthetic substrate. 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 PubMedPhosphotriesterase, as isolated from Pseudomonas diminuta, is capable of detoxifying widely used pesticides such as paraoxon and parathion and various mammalian acetylcholinesterase inhibitors. The enzyme requires a binuclear metal center for activity. Recently, the three-dimensional structure of the apoenzyme was solved (Benning et al., 1994) and shown to consist of an alpha/beta-barrel. Here we describe the three-dimensional structure of the holoenzyme, reconstituted with cadmium, as determined by X-ray crystallographic analysis to 2.0-A resolution. Crystals employed in the investigation belonged to the space group C2 with unit cell dimensions of a = 129.5 A, b = 91.4 A, c = 69.4 A, beta = 91.9 degrees, and two subunits in the asymmetric unit. There are significant differences in the three-dimensional architecture of the apo and holo forms of the enzyme such that their alpha-carbon positions superimpose with a root-mean-square deviation of 3.4 A. The binuclear metal center is located at the C-terminus of the beta-barrel with the cadmiums separated by 3.8 A. There are two bridging ligands to the metals: a water molecule (or possibly a hydroxide ion) and a carbamylated lysine residue (Lys 169). The more buried cadmium is surrounded by His 55, His 57, Lys 169, Asp 301, and the bridging water in a trigonal bipyramidal arrangement. The second metal is coordinated in a distorted octahedral geometry by His 201, His 230, Lys 169, the bridging water molecule, and two additional solvents. Three-dimensional structure of the binuclear metal center of phosphotriesterase.,Benning MM, Kuo JM, Raushel FM, Holden HM Biochemistry. 1995 Jun 27;34(25):7973-8. PMID:7794910[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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