title: The Methanocaldococcus jannaschii protein Mj0968 is not a P-type ATPase.
abstract: The Methanocaldococcus jannaschii (formerly Methanococcus jannaschii) protein Mj0968 has been reported to represent a soluble P-type ATPase [Ogawa et al., FEBS Lett. 471 (2000) 99-102]. In this study, we report that the heterologously expressed Mj0968-His(10) protein exhibits high rates of phosphatase activity, whereas only very low ATPase activity was measured. Replacement of the aspartate residue in the DSAGT motif (D7A), which becomes phosphorylated during the reaction cycle of P-type ATPases, does not affect the V(max), but only the K(M) of the reaction. Labeling studies with [gamma-(32)P]ATP and [alpha-(32)P]ATP revealed that the previously reported labeling experiments [Ogawa et al., 2000] do not necessarily show phosphorylation of Mj0968, but rather point to ATP binding. Binding studies with trinitrophenyl adenosine nucleotides showed low apparent K(d) values for those molecules. These results provide evidence that the native function of Mj0968 seems to be that of a phosphatase, rather than that of an ATP-hydrolyzing enzyme.
authors.affiliation: Universität Osnabrück, Fachbereich Biologie/Chemie, Abteilung Mikrobiologie, D-49069, Osnabrück, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Bramkamp
authors.forename: Michael
authors.initials: M
authors.lastname: Gassel
authors.forename: Brigitte
authors.initials: B
authors.lastname: Herkenhoff-Hesselmann
authors.forename: Jessica
authors.initials: J
authors.lastname: Bertrand
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Altendorf
mesh_terms: D000227:Adenine Nucleotides / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D003001:Cloning, Molecular; D007700:Kinetics; D017017:Methanococcus / Q000201:enzymology*; D010744:Phosphoric Monoester Hydrolases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism; D014301:Trinitrobenzenes / Q000378:metabolism
chemical_list: D000227:Adenine Nucleotides; D011993:Recombinant Fusion Proteins; D014301:Trinitrobenzenes; D000255:Adenosine Triphosphate; D010744:Phosphoric Monoester Hydrolases; D000251:Adenosine Triphosphatases