Functional analyses of bacterial nucleotide transport proteins

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Exploitation of host derived nucleotides and “energy parasitism” are essential common features of certain obligate intracellular (pathogenic) bacteria. Although various nucleotide transport proteins (NTT) have been characterized so far, fundamental questions concerning biochemical properties and structure/function relationships remained unaddressed. Our very recent analyses provided evidence for phosphate as a previously unidentified substrate of the ATP/ADP transporter PamNTT1 from the amoeba symbiont Protochlamydia amoebophila. Interestingly, an NTT driven phosphate transport would make a specialized phosphate carrier unnecessary and would explain why the long lasting search for the corresponding protein in intracellular living bacteria failed. In this study, we will perform a sophisticated biochemical analysis of the functionally different nucleotide transporters PamNTT1-5 and also of a representative ATP/ADP transporter from Rickettsiales which aims to clarify whether bacterial phosphate transport is (i) restricted to PamNTT1 or (ii) a typical feature of “energy parasitism” or (iii) a general principle in bacterial nucleotide transport. Furthermore, by the help of selected mutant proteins we aim to identify amino acids essential for nucleotide and phosphate transport.