1tzm

Crystal structure of ACC deaminase complexed with substrate analog b-chloro-D-alanine

spinqualitylabelsall models 1tzm, resolution 2.08Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1tzm is a 4 chain structure with sequence from Pseudomonas sp. ACP. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.08Å Ligands: C2N, NAK, PLP, SO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function 1A1D_PSEUD 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 PubMed 1-Aminocyclopropane-1-carboxylate (ACC) deaminase is a pyridoxal 5'-phosphate (PLP) dependent enzyme catalyzing the opening of the cyclopropane ring of ACC to give alpha-ketobutyric acid and ammonia as the products. This ring cleavage reaction is unusual because the substrate, ACC, contains no abstractable alpha-proton and the carboxyl group is retained in the product. How the reaction is initiated to generate an alpha-carbanionic intermediate, which is the common entry for most PLP-dependent reactions, is not obvious. To gain insight into this unusual ring-opening reaction, we have solved the crystal structures of ACC deaminase from Pseudomonas sp. ACP in complex with substrate ACC, an inhibitor, 1-aminocyclopropane-1-phosphonate (ACP), the product alpha-ketobutyrate, and two d-amino acids. Several notable observations of these structural studies include the following: (1) a typically elusive gem-diamine intermediate is trapped in the enzyme complex with ACC or ACP; (2) Tyr294 is in close proximity (3.0 A) to the pro-S methylene carbon of ACC in the gem-diamine complexes, implicating a direct role of this residue in the ring-opening reaction; (3) Tyr294 may also be responsible for the abstraction of the alpha-proton from d-amino acids, a prelude to the subsequent deamination reaction; (4) the steric hindrance precludes accessibility of active site functional groups to the l-amino acid substrates and may account for the stereospecificity of this enzyme toward d-amino acids. These structural data provide evidence favoring a mechanism in which the ring cleavage is induced by a nucleophilic attack at the pro-S beta-methylene carbon of ACC, with Tyr294 as the nucleophile. However, these observations are also consistent with an alternative mechanistic possibility in which the ring opening is acid-catalyzed and may be facilitated by charge relay through PLP, where Tyr294 functions as a general acid. The results of mutagenesis studies corroborated the assigned critical role for Tyr294 in the catalysis. Structural analysis of Pseudomonas 1-aminocyclopropane-1-carboxylate deaminase complexes: insight into the mechanism of a unique pyridoxal-5'-phosphate dependent cyclopropane ring-opening reaction.,Karthikeyan S, Zhou Q, Zhao Z, Kao CL, Tao Z, Robinson H, Liu HW, Zhang H Biochemistry. 2004 Oct 26;43(42):13328-39. PMID:15491139 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Deaminase 3D structures

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