title: Co2+ selectivity of Thermotoga maritima CorA and its inability to regulate Mg2+ homeostasis present a new class of CorA proteins.
abstract: CorA is a family of divalent cation transporters ubiquitously present in bacteria and archaea. Although CorA can transport both Mg(2+) and Co(2+) almost equally well, its main role has been suggested to be that of primary Mg(2+) transporter of prokaryotes and hence the regulator of Mg(2+) homeostasis. The reason is that the affinity of CorA for Co(2+) is relatively low and thus considered non-physiological. Here, we show that Thermotoga maritima CorA (TmCorA) is incapable of regulating the Mg(2+) homeostasis and therefore cannot be the primary Mg(2+) transporter of T. maritima. Further, our in vivo experiments confirm that TmCorA is a highly selective Co(2+) transporter, as it selects Co(2+) over Mg(2+) at >100 times lower concentrations. In addition, we present data that show TmCorA to be extremely thermostable in the presence of Co(2+). Mg(2+) could not stabilize the protein to the same extent, even at high concentrations. We also show that addition of Co(2+), but not Mg(2+), specifically induces structural changes to the protein. Altogether, these data show that TmCorA has the role of being the transporter of Co(2+) but not Mg(2+). The physiological relevance and requirements of Co(2+) in T. maritima is discussed and highlighted. We suggest that CorA may have different roles in different organisms. Such functional diversity is presumably a reflection of minor, but important structural differences within the CorA family that regulate the gating, substrate selection, and transport.
authors: Biomedical Structural Biology, School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
authors: Yu
authors: Y
authors: Xia
authors: Anna-Karin
authors: AK
authors: Lundbäck
authors: Newsha
authors: N
authors: Sahaf
authors: Gustav
authors: G
authors: Nordlund
authors: Peter
authors: P
authors: Brzezinski
authors: Said
authors: S
authors: Eshaghi
mesh_terms: D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D003035:Cobalt / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology*; D008274:Magnesium / Q000378:metabolism*; D020124:Thermotoga maritima / Q000235:genetics / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D003035:Cobalt; D008274:Magnesium