title: Functional insights from the molecular modelling of a novel two-component system.
abstract: Two-component systems (TCSs) are the major signalling pathway in bacteria and represent potential drug targets. Among the 11 paired TCS proteins present in Mycobacterium tuberculosis H37Rv, the histidine kinases (HKs) Rv0600c (HK1) and Rv0601c (HK2) are annotated to phosphorylate one response regulator (RR) Rv0602c (TcrA). We wanted to establish the sequence-structure-function relationship to elucidate the mechanism of phosphotransfer using in silico methods. Sequence alignments and codon usage analysis showed that the two domains encoded by a single gene in homologous HKs have been separated into individual open-reading frames in M. tuberculosis. This is the first example where two incomplete HKs are involved in phosphorylating a single RR. The model shows that HK2 is a unique histidine phosphotransfer (HPt)-mono-domain protein, not found as lone protein in other bacteria. The secondary structure of HKs was confirmed using "far-UV" circular dichroism study of purified proteins. We propose that HK1 phosphorylates HK2 at the conserved H131 and the phosphoryl group is then transferred to D73 of TcrA.
authors.affiliation: Department of Biotechnology, Indian Institute of Technology, Kharagpur 721302, India.
authors.forename: Rashmi
authors.initials: R
authors.lastname: Shrivastava
authors.forename: Dibya Ranjan
authors.initials: DR
authors.lastname: Das
authors.forename: Harald G
authors.initials: HG
authors.lastname: Wiker
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Das
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification; D019295:Computational Biology; D000071677:Histidine Kinase; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D016366:Open Reading Frames; D010766:Phosphorylation; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D011494:Protein Kinases / Q000737:chemistry* / Q000302:isolation & purification; D015398:Signal Transduction; D015534:Trans-Activators / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D001426:Bacterial Proteins; D015534:Trans-Activators; C112177:osmolarity response regulator proteins; D011494:Protein Kinases; D000071677:Histidine Kinase