title: A potentially versatile nucleotide hydrolysis activity of group II chaperonin monomers from Thermoplasma acidophilum.
abstract: Compared to the group I chaperonins such as Escherichia coli GroEL, which facilitate protein folding, many aspects of the functional mechanism of archaeal group II chaperonins are still unclear. Here, we show that monomeric forms of archaeal group II chaperonin alpha and beta from Thermoplasma acidophilum may be purified stably and that these monomers display a strong AMPase activity in the presence of divalent ions, especially Co(2+) ion, in addition to ATPase and ADPase activities. Furthermore, other nucleoside phosphates (guanosine, cytidine, uridine, and inosine phosphates) in addition to adenine nucleotides were hydrolyzed. From analyses of the products of hydrolysis using HPLC, it was revealed that the monomeric chaperonin successively hydrolyzed the phosphoanhydride and phosphoester bonds of ATP in the order of gamma to alpha. This activity was strongly suppressed by point mutation of specific essential aspartic acid residues. Although these archaeal monomeric chaperonins did not alter the refolding of MDH, their novel versatile nucleotide hydrolysis activity might fulfill a new function. Western blot experiments demonstrated that the monomeric chaperonin subunits were also present in lysed cell extracts of T. acidophilum, and partially purified native monomer displayed Co(2+)-dependent AMPase activity.
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, Institute of Regenerative Medicine Biofunction, Graduate School of Medical Science, Tottori University, Tottori 680-8552, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Noi
authors.forename: Hidenori
authors.initials: H
authors.lastname: Hirai
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Hongo
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Mizobata
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kawata
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry / Q000378:metabolism*; D018833:Chaperonins / Q000737:chemistry / Q000378:metabolism*; D006868:Hydrolysis; D009708:Nucleotidases / Q000737:chemistry / Q000378:metabolism; D009711:Nucleotides / Q000737:chemistry / Q000378:metabolism*; D010710:Phosphates / Q000737:chemistry; D017510:Protein Folding; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013822:Thermoplasma / Q000201:enzymology / Q000378:metabolism*
chemical_list: D019843:Archaeal Proteins; D009711:Nucleotides; D010710:Phosphates; D021122:Protein Subunits; D011994:Recombinant Proteins; D009708:Nucleotidases; C018775:adenosine monophosphatase; D018833:Chaperonins