Functional similarity between archaeal and bacterial CorA magnesium transporters

Abstract

The constitutively expressed Cora Mg2+ transporter is the major Mg2+ 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 Mg2+-transport-deficient strain of S. typhimurium to determine its functional characteristics. The archaeal Cora homolog is a functional Mg2+ 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.