title: C-terminal tail derived from the neighboring subunit is critical for the activity of Thermoplasma acidophilum D-aldohexose dehydrogenase.
abstract: The D-aldohexose dehydrogenase from the thermoacidophilic archaeon Thermoplasma acidophilum (AldT) is a homotetrameric enzyme that catalyzes the oxidation of several D-aldohexoses, especially D-mannose. AldT comprises a unique C-terminal tail motif (residues 247-255) that shuts the active-site pocket of the neighboring subunit. The functional role of the C-terminal tail of AldT has been investigated using mutational and crystallographic analyses. A total of four C-terminal deletion mutants (Delta254, Delta253, Delta252, and Delta249) and two site-specific mutants (Y86G and P254G) were expressed by Escherichia coli and purified. Enzymatic characterization of these mutants revealed that the C-terminal tail is a requisite and that the interaction between Tyr86 and Pro254 is critical for enzyme activity. The crystal structure of the Delta249 mutant was also determined. The structure showed that the active-site loops undergo a significant conformational change, which leads to the structural deformation of the substrate-binding pocket.
authors.affiliation: Laboratory of Molecular Environmental Microbiology, Graduate School of Agriculture, Hokkaido University, Kita-ku, Sapporo 060-8589, Japan.
authors.forename: Taiki
authors.initials: T
authors.lastname: Nishioka
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Yasutake
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nishiya
authors.forename: Noriko
authors.initials: N
authors.lastname: Tamura
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Tamura
mesh_terms: D001665:Binding Sites; D002237:Carbohydrate Dehydrogenases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D011392:Proline / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D013822:Thermoplasma / Q000201:enzymology*; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism
chemical_list: D021122:Protein Subunits; D014443:Tyrosine; D011392:Proline; D002237:Carbohydrate Dehydrogenases; C501231:aldohexose dehydrogenase