9.B.69 The Putative Cobalt Transporter (CbtAB) Family
The putative cobalt transporter family consists of two proteins, one (CbtA) of about 230 aas with 6 TMSs, and one (CbtB) of about 70 (60-150) residues, with a single putative TMS. CbtB is possibly a periplasmic or membrane anchored Co2+binding protein. However, some of the larger homologues have the putative TMS at their C-termini. These proteins are encoded in operons that are subject to regulation by vitamin B12 (Rodionov et al., 2003). They are found in α- and γ-proteobacteria. Their functions are not established.