Identification and characterization of ABC transporters for carbohydrate uptake in Thermus thermophilus HB8

Organisms use a variety of carbohydrates and metabolic pathways in order to capitalize in their specific environments. Depending upon their habitat, organism employs different types of transporters to maintain the cellular nutritional balance via central metabolism. A major contributor in this process in bacteria is a carbohydrate ABC transporter. The focus of this study is to get an insight into the carbohydrate transport and metabolism of a hot-spring-dwelling bacterium Thermus thermophilus HB8. We applied high-throughput data-mining approaches for identification and characterization of carbohydrate ABC transporters in T. thermophilus HB8. This enabled the identification of 11 putative carbohydrate ABC transport systems. To identify the cognate ligands for these transporters, functional annotation was performed. However, scarcity of homologous-protein's function hinders the process of functional annotation. Thus, to overcome this limitation, we integrated the functional annotation of carbohydrate ABC transporters with their metabolic analysis. Our results demonstrate that out of 11 putative carbohydrate ABC transporters, six are involved in the sugar (four for monosaccharides and polysaccharides-degraded products and two for osmotic regulation), four in phospholipid precursor (namely UgpABCE) and the remaining one in purine uptake. Further, analysis suggests the existence of sharing mechanism of transmembrane domains (TMDs) and/or nucleotide-binding domains (NBDs) among the 11 carbohydrate ABC transporters.