Functional Similarity between Archaeal and Bacterial CorA Magnesium Transporters

Abstract

ABSTRACT 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.