PHYLOGENETIC ANALYSES OF THE ATP-BINDING CONSTITUENTS OF BACTERIAL EXTRACYTOPLASMIC RECEPTOR-DEPENDENT ABC-TYPE NUTRIENT-UPTAKE PERMEASES

Thirty-eight ATP-binding cassette (ABC) protein constituents of bacter ial extracytoplasmic receptor-dependent nutrient uptake systems, inclu ding one homologous chloroplast protein were analysed for sequence con servation and phylogenetic relatedness. The proteins were generally fo und to cluster in accordance with the clustering patterns previously o bserved for the extracytoplasmic receptors and the transmembrane chann el-forming constituents of these permeases. The results suggest that t hese transport systems evolved from a single primordial system with mi nimal shuffling of the three dissimilar protein constituents of the sy stems.