Elucidation of the role of Ser329 and the C-terminal region in the catalytic activity of Pseudomonas stutzeri L-rhamnose isomerase.
Pseudomonas stutzeri l-rhamnose isomerase (l-RhI) is capable of catalyzing the isomerization between various aldoses and ketoses, showing high catalytic activity with broad substrate-specificity compared with Escherichia coli l-RhI. In a previous study, the crystal structure of P. stutzeri l-RhI revealed an active site comparable with that of E. coli l-RhI and d-xylose isomerases (d-XIs) with structurally conserved amino acids, but also with a different residue seemingly responsible for the specificity of P. stutzeri l-RhI, though the residue itself does not interact with the bound substrate. This residue, Ser329, corresponds to Phe336 in E. coli l-RhI and Lys294 in Actinoplanes missouriensis d-XI. To elucidate the role of Ser329 in P. stutzeri l-RhI, we constructed mutants, S329F (E. coli l-RhI type), S329K (A. missouriensis d-XI type), S329L and S329A. Analyses of the catalytic activity and crystal structure of the mutants revealed a hydroxyl group of Ser329 to be crucial for catalytic activity via interaction with a water molecule. In addition, in complexes with substrate, the mutants S329F and S329L exhibited significant electron density in the C-terminal region not observed in the wild-type P. stutzeri l-RhI. The C-terminal region of P. stutzeri l-RhI has flexibility and shows a flip-flop movement at the inter-molecular surface of the dimeric form.
Division of Structural Biology, Life Science Research Center and Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0793, Japan.
Hiromi
H
Yoshida
Kosei
K
Takeda
Ken
K
Izumori
Shigehiro
S
Kamitori
D019747:Aldose-Ketose Isomerases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055162:Biocatalysis; D020134:Catalytic Domain; D004926:Escherichia coli / Q000201:enzymology; D006601:Hexoses / Q000737:chemistry / Q000378:metabolism; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary; D044223:Pseudomonas stutzeri / Q000201:enzymology* / Q000235:genetics; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D014961:X-Ray Diffraction
D001426:Bacterial Proteins; D006601:Hexoses; D012694:Serine; D019747:Aldose-Ketose Isomerases; C062878:L-rhamnose isomerase