title: Structural insight into gene duplication, gene fusion and domain swapping in the evolution of PLP-independent amino acid racemases.
abstract: The X-ray crystal structure has revealed two similar alpha/beta domains of aspartate racemase (AspR) from Pyrococcus horikoshii OT3, and identified a pseudo mirror-symmetric distribution of the residues around its active site [Liu et al. (2002) J. Mol. Biol. 319, 479-489]. Structural homology and functional similarity between the two domains suggested that this enzyme evolved from an ancestral domain by gene duplication and gene fusion. We have expressed solely the C-terminal domain of this AspR and determined its three-dimensional structure by X-ray crystallography. The high structural stability of this domain supports the existence of the ancestral domain. In comparison with other amino acid racemases (AARs), we suggest that gene duplication and gene fusion are conventional ways in the evolution of pyridoxal 5'-phosphate-independent AARs.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Japan.
authors.forename: Lijun
authors.initials: L
authors.lastname: Liu
authors.forename: Kousuke
authors.initials: K
authors.lastname: Iwata
authors.forename: Masafumi
authors.initials: M
authors.lastname: Yohda
authors.forename: Kunio
authors.initials: K
authors.lastname: Miki
mesh_terms: D000591:Amino Acid Isomerases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D019677:Artificial Gene Fusion; D001483:Base Sequence; D018360:Crystallography, X-Ray; D004269:DNA, Bacterial / Q000235:genetics; D004795:Enzyme Stability; D019143:Evolution, Molecular; D020440:Gene Duplication; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011732:Pyridoxal Phosphate / Q000378:metabolism; D019711:Pyrococcus / Q000201:enzymology / Q000235:genetics; D017386:Sequence Homology, Amino Acid
chemical_list: D004269:DNA, Bacterial; D011732:Pyridoxal Phosphate; D000591:Amino Acid Isomerases; C019749:aspartate racemase