Functional Similarity between Archaeal and Bacterial CorA Magnesium Transporters

The constitutively expressed CorA Mg(2+) transporter is the major Mg(2+) influx system of Salmonella typhimurium and Escherichia coli. Genomic sequence data indicated the presence of a homolog in the archaeal organism Methanococcus jannaschii. The putative M. jannaschii CorA was expressed in an Mg(2+)-transport-deficient strain of S. typhimurium to determine its functional characteristics. The archaeal CorA homolog is a functional Mg(2+) uptake system when expressed in S. typhimurium and has properties which are highly similar to those of the normal CorA transporter of S. typhimurium despite having a low level of sequence identity with the protein and being expressed in a lipid membrane of quite different composition than normal. This implies that the overall function of the proteins is the same and further suggests that their structures are very similar.