HstK, a cyanobacterial protein with both a serine/threonine kinase domain and a histidine kinase domain: implication for the mechanism of signal transduction.
Two distinct families of protein kinases are involved in signal transduction: Ser, Thr and Tyr kinases, which are predominantly found among eukaryotes, and His kinases, as part of bacterial two-component signalling systems. Genetic studies in Arabidopsis and Saccharomyces have demonstrated that bacterial-type two-component systems may act upstream of Ser/Thr kinases in the same signalling pathway, but how this coupling is accomplished remains unclear. In the present study, we report the characterization of a protein kinase, HstK, from the N(2)-fixing cyanobacterium Anabaena sp. PCC 7120, that possesses both a Ser/Thr kinase domain and a His kinase domain. Proteins with a structural architecture similar to that of HstK can be found in the eukaryote, Schizosaccharomyces pombe, and the bacterium, Rhodococcus sp. M5. HstK was present in cells grown with NH(4)(+) or N(2) as the nitrogen source, but was absent in cells grown with NO(3)(-). The hstK gene was inactivated and the mutant phenotype was characterized. The catalytic domain of the Ser/Thr kinase of HstK functionally replaced that of Hog1p, a well-characterized protein kinase required for the response to high osmolarity in the S. cerevisiae heterologous system. The unusual multidomain structure of HstK suggests that a two-component system could be directly coupled to Ser/Thr kinases in the same signal transduction pathway.
Phalip
V
V
Unité d'Immunotechnologie et Microbiologie Moléculaire, Ecole Superieure de Biotechnologie de Strasbourg, Université Louis Pasteur de Strasbourg, Boulevard Sebastien Brandt, F-67400 Illkirch, France.
Li
J H
JH
Zhang
C C
CC
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000458:Cyanobacteria / Q000201:enzymology*; D030562:Databases, Protein; D000071677:Histidine Kinase; D007700:Kinetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology*
D001426:Bacterial Proteins; D011994:Recombinant Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D000071677:Histidine Kinase