The Insertional Inactivation of Genes Encoding Eukaryotic-Type Serine/Threonine Protein Kinases in the Cyanobacterium Synechocystis sp. PCC 6803

Synechocystis sp. PCC 6803 mutants, in which one of the eukaryotic-type serine/threonine protein kinase genes pknD, pknE, pknG, and pknH was inactivated, were obtained by insertion mutagenesis. None of these mutants differed phenotypically from the wild-type strain, indicating that the pknD, pknE, pknG, and pknHgenes are not of crucial importance for the photoautotrophically grown cyanobacterium. The mutant with the inactivatedpknE gene was resistant to L-methionine-D,L-sulfoximine and especially to methylamine. The resistance was due neither to the impaired transport of these compounds nor to the inhibition of the production of toxic -glutamylmethylamide from methylamine. The data presented suggest that resistance to methylamine may be associated with alterations in the regulation of the glutamine synthetase system and that the PknE protein kinase may be involved in the regulation of nitrogen metabolism in the cyanobacterium studied.