The amino acid sequences of the periplasmic binding protein and the two membrane-bound transport proteins which comprise the complete dicarboxylate transporting system of E. coli will be determined using automated protein sequencing methods. The production of the membrane-bound proteins may be enhanced by amplifying the genes for the proteins using recombinant DNA techniques. The sequences of the ribose and citrate binding proteins will be completed. The sequence changes in a number of functionally defective mutant galactose and arabinose binding proteins will be determined using our new HPLC mapping procedure. The structures of the dicarboxylate transport system components will be the base from which a description of the sequence of molecular events taking place during membrane transport can be built. The data from the citrate and ribose binding protein sequences together with those from the studies on the mutant binding proteins will be compared to the sequence and X-ray structures already determined for several other binding proteins to yield a detaied structure-function analysis of these proteins. This should ultimately make it possible to delineate in chemical terms the steps by which the binding proteins interact with the membrane-bound transport systems and deliver nutrients to the cell membrane.
