title: Allosteric activation by dimerization of the PknD receptor Ser/Thr protein kinase from Mycobacterium tuberculosis.
abstract: To define how extracellular signals activate bacterial receptor Ser/Thr protein kinases, we characterized the regulatory functions of a weak dimer interface identified in the Mycobacterium tuberculosis PknB and PknE receptor kinases. Sequence comparisons revealed that the analogous interface is conserved in PknD orthologs from diverse bacterial species. To analyze the roles of dimerization, we constructed M. tuberculosis PknD kinase domain (KD) fusion proteins that formed dimers upon addition of rapamycin. Dimerization of unphosphorylated M. tuberculosis PknD KD fusions stimulated phosphorylation activity. Mutations in the dimer interface reduced this activation, limited autophosphorylation, and altered substrate specificity. In contrast, an inactive catalytic site mutant retained the ability to stimulate the wild-type KD by dimerization. These results support the idea that dimer formation allosterically activates unphosphorylated PknD. The phosphorylated PknD KD was fully active even in the absence of dimerization, suggesting that phosphorylation provides an additional regulatory mechanism. The conservation of analogous dimers in diverse prokaryotic and eukaryotic Ser/Thr protein kinases implies that this mechanism of protein kinase regulation is ancient and broadly distributed.
authors.affiliation: Department of Molecular and Cell Biology, and Howard Hughes Medical Institute Mass Spectrometry Laboratory, University of California, Berkeley, California 94720-3206, USA.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Greenstein
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Echols
authors.forename: T Noelle
authors.initials: TN
authors.lastname: Lombana
authors.forename: David S
authors.initials: DS
authors.lastname: King
authors.forename: Tom
authors.initials: T
authors.lastname: Alber
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D002384:Catalysis; D019281:Dimerization; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D013379:Substrate Specificity
chemical_list: D011494:Protein Kinases; C112455:PknD protein, Nostoc sp. PCC 7120; D017346:Protein Serine-Threonine Kinases