title: Forkhead-associated domain-containing protein Rv0019c and polyketide-associated protein PapA5, from substrates of serine/threonine protein kinase PknB to interacting proteins of Mycobacterium tuberculosis.
abstract: Mycobacterium tuberculosis profoundly exploits protein phosphorylation events carried out by serine/threonine protein kinases (STPKs) for its survival and pathogenicity. Forkhead-associated domains (FHA), the phosphorylation-responsive modules, have emerged as prominent players in STPK mediated signaling. In this study, we demonstrate the association of the previously uncharacterized FHA domain-containing protein Rv0019c with cognate STPK PknB. The consequent phosphorylation of Rv0019c is shown to be dependent on the conserved residues in the Rv0019c FHA domain and activation loop of PknB. Furthermore, by creating deletion mutants we identify Thr(36) as the primary phosphorylation site in Rv0019c. During purification of Rv0019c from Escherichia coli, the E. coli protein chloramphenicol acetyltransferase (CAT) specifically and reproducibly copurifies with Rv0019c in a FHA domain-dependent manner. On the basis of structural similarity of E. coli CAT with M. tuberculosis PapA5, a protein involved in phthiocerol dimycocerosate biosynthesis, PapA5 is identified as an interaction partner of Rv0019c. The interaction studies on PapA5, purified as an unphosphorylated protein from E. coli, with Rv0019c deletion mutants reveal that the residues N-terminal to the functional FHA domain of Rv0019c are critical for formation of the Rv0019c-PapA5 complex and thus constitute a previously unidentified phosphoindependent binding motif. Finally, PapA5 is shown to be phosphorylated on threonine residue(s) by PknB, whereas serine/threonine phosphatase Mstp completely reverses the phosphorylation. Thus, our data provides initial clues for a possible regulation of PapA5 and hence the phthiocerol dimycocerosate biosynthesis by PknB, either by direct phosphorylation of PapA5 or indirectly through Rv0019c.
authors.affiliation: Institute of Genomics and Integrative Biology, Council of Scientific and Industrial Research, Delhi 110007, India.
authors.forename: Meetu
authors.initials: M
authors.lastname: Gupta
authors.forename: Andaleeb
authors.initials: A
authors.lastname: Sajid
authors.forename: Gunjan
authors.initials: G
authors.lastname: Arora
authors.forename: Vibha
authors.initials: V
authors.lastname: Tandon
authors.forename: Yogendra
authors.initials: Y
authors.lastname: Singh
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D051858:Forkhead Transcription Factors; D010750:Phosphoproteins; D000217:Acyltransferases; C487811:PapA5 protein, Mycobacterium tuberculosis; C475060:PknB protein, Mycobacterium tuberculosis; D017346:Protein Serine-Threonine Kinases