This family is comprised of systems involved in the uptake of various metallic cations such as iron, manganese and zinc. Putative systems belonging to the MET family were found in the genomes of prokaryotes and in the cyanelle genome of the photoautotrophic protist Cyanophora paradoxa. The ATPases of these systems are strongly related to that of iron-siderophore uptake systems (ISVH family) suggesting that they arose from a common ancestor ( Pubmed : 9873074 ) . Weaker but significant similarities could be detected between IM of the MET and ISVH families. In Streptococcus pneumoniae, mutations in the adc and psa loci, that determine 2 MET family systems involved in the uptake of zinc and manganese respectively, affect competence and virulence ( Pubmed : 9379902 ) .