J. Phys. IV France 07 (1997) C1-651-C1-654
Genetic Analysis of Biomagnetic Crystal FormationT. Matsunaga1, N. Tsujimura1 and S. Kamiya2
1 Department of Biotechnology, Tokyo University of Agriculture & Technology, 2-24-16, Naka-cho, Koganei-shi, Tokyo 184, Japan
2 TDK Akita Laboratory Corporation, 15 Aza-Gashomen, Hirasawa, Nikaho-machi, Yuri-gun, Akita 018-04, Japan
Magnetospirillum sp. AMB-1 is a freshwater magnetic bacterium which synthesizes intracellular particles of magnetite (Fe3O4). A genomic DNA fragment required for synthesis of magnetic particles was previously isolated from a non-magnetic transposon Tn5 mutant. We have determined the complete nucleotide sequence of this fragment. The 2975 bp region contains two putative open reading frames (ORFs). One ORF, designated magA, encodes a polypeptide which is homologous to the cation efflux proteins, the Escherichia coli potassium ion translocating protein, KefC, and the putative Na+/H+-antiporter, NapA, from Enterococcus hirae. Intracellular localization of the MagA protein was studied using magA - luc fusion proteins. The luc gene was cloned downstream of the magA hydrophilic C-terminal domain. The fusion protein was also detected on the surface of the lipid bilayer covering the magnetic particles. These results suggest that MagA is a membrane-bound protein. Vesicles which contained MagA protein exhibited iron accumulation ability. We consider that the MagA protein is an iron transporter involved in the synthesis of magnetic particles in AMB-1.
© EDP Sciences 1997