EVIDENCE FOR 2 TYPES OF SUBUNITS IN THE BACTERIOFERRITIN OF MAGNETOSPIRILLUM-MAGNETOTACTICUM

In order to investigate the role of bacterioferritin (Bfr) in the biom ineralization of magnetite by microorganisms, we have cloned and seque nced the bfr genes from M. magnetotacticum. The organism has two bfr g enes that overlap by one nucleotide. Both encode putative protein prod ucts of 18 kDa, the expected size for Bfr subunits, and show a strong similarity to other Bfr subunit proteins. By scanning the DNA sequence databases, we found that a limited number of other organisms, includi ng N. gonorrhea, P. aeruginosa, and Synechocystis PCC6803, also have t wo bfr genes. When the sequences of a number of microbial Bfrs are com pared with each other, they fall into two distinct types with the orga nisms mentioned above having one of each type. Differences in heme-and metal-binding sites and ferroxidase activities of the two types of su bunits are discussed. (C) 1997 Elsevier Science B.V.