title: A magnetosome-specific GTPase from the magnetic bacterium Magnetospirillum magneticum AMB-1.
abstract: Magnetic bacteria produce intracellular vesicles that envelope single domain magnetite crystals. Although many proteins are present in this intracellular vesicle membrane, five are specific to this membrane. A 16-kDa protein, designated Mms16, is the most abundant of the magnetosome-specific proteins, and to establish its function we cloned and sequenced its gene from Magnetospirillum magneticum AMB-1. This was achieved by determination of the N-terminal amino acid sequence of the protein following two dimensional polyacrylamide gel electrophoresis, and sequencing of the gene was performed by gene walking using anchored polymerase chain reaction. Mms16 contains a putative ATP/GTP binding motif (P-loop). Recombinant Mms16 with a hemagglutinin tag, was expressed in Escherichia coli and purified. Recombinant Mms16 protein could bind GTP and showed GTPase activity. GTP was the preferred substrate for Mms16-catalyzed nucleotide triphosphate hydrolysis. These results suggest that a novel protein specifically localized on the magnetic particle membrane, Mms16, is a GTPase. Mms16 protein showed similar characteristics to small GTPases involved in the formation of intracellular vesicles. Furthermore, addition of the GTPase inhibitor AlF(4)- also inhibited magnetic particle synthesis, suggesting that GTPase is required for magnetic particles synthesis.
authors.affiliation: Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Okamura
authors.forename: H
authors.initials: H
authors.lastname: Takeyama
authors.forename: T
authors.initials: T
authors.lastname: Matsunaga
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D017931:DNA Primers; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D008280:Magnetics; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D011485:Protein Binding; D012244:Rhodospirillaceae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases; C445324:Mms16 protein, Magnetospirillum magneticum