1jfl

CRYSTAL STRUCTURE DETERMINATION OF ASPARTATE RACEMASE FROM AN ARCHAEA

spinqualitylabelsall models 1jfl, resolution 1.90Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1jfl is a 2 chain structure with sequence from Pyrococcus horikoshii. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Gene: PH0670 (Pyrococcus horikoshii) Activity: Aspartate racemase, with EC number 5.1.1.13 Resources: FirstGlance, OCA, RCSB, PDBsum 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 There exists a d-enantiomer of aspartic acid in lactic acid bacteria and several hyperthermophilic archaea, which is biosynthesized from the l-enantiomer by aspartate racemase. Aspartate racemase is a representative pyridoxal 5'-phosphate (PLP)-independent amino acid racemase. The "two-base" catalytic mechanism has been proposed for this type of racemase, in which a pair of cysteine residues are utilized as the conjugated catalytic acid and base. We have determined the three-dimensional structure of aspartate racemase from the hyperthermophilic archaeum Pyrococcus horikoshii OT3 at 1.9 A resolution by X-ray crystallography and refined it to a crystallographic R factor of 19.4% (R(free) of 22.2%). This is the first structure reported for aspartate racemase, indeed for any amino acid racemase from archaea. The crystal structure revealed that this enzyme forms a stable dimeric structure with a strong three-layered inter-subunit interaction, and that its subunit consists of two structurally homologous alpha/beta domains, each containing a four-stranded parallel beta-sheet flanked by six alpha-helices. Two strictly conserved cysteine residues (Cys82 and Cys194), which have been shown biochemically to act as catalytic acid and base, are located on both sides of a cleft between the two domains. The spatial arrangement of these two cysteine residues supports the "two-base" mechanism but disproves the previous hypothesis that the active site of aspartate racemase is located at the dimeric interface. The structure revealed a unique pseudo mirror-symmetry in the spatial arrangement of the residues around the active site, which may explain the molecular recognition mechanism of the mirror-symmetric aspartate enantiomers by the non-mirror-symmetric aspartate racemase. Crystal structure of aspartate racemase from Pyrococcus horikoshii OT3 and its implications for molecular mechanism of PLP-independent racemization.,Liu L, Iwata K, Kita A, Kawarabayasi Y, Yohda M, Miki K J Mol Biol. 2002 May 31;319(2):479-89. PMID:12051922 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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