Characterization of Glutamine Synthetase and ATPases in a Mutant Strain of the Cyanobacterium Nostoc muscorum Capable of Metabolizing Methylamine as a Source of Nitrogen

Photoautotrophic growth, photosynthetic O₂-evolution and the activity of Ca²⁺-dependent ATPase and Mg²⁺-dependent ATPase of parental Nostoc muscorum were inhibited by methylamine. Mutant of the parental strain capable of growth in the presence of growth inhibitory concentration of methylamine lacked all these inhibitory effects of the analogue as observed in the parental strain. The in vitro Glutamine Synthetase activity of both the strains was found similar with respect to L-Methionine-DL-Sulfoximine sensitivity. The parental strain showed Methylammonium sensitive activities of Ca²⁺-dependent ATPase and Mg²⁺-dependent ATPase. The mutant strain produced methylamine resistant Ca²⁺-dependent ATPase and Mg²⁺-dependent ATPase. The ability of the mutant strain to assimilate methylamine like a fixed nitrogen source, thus appears to be the result of mutation causing production of Ca²⁺-dependent ATPase and Mg²⁺-dependent ATPase resistant to inhibitory effect of methylamine. While production of methylamine-resistant Mg²⁺-dependent ATPase appeared constitutive, that of Ca²⁺-dependent ATPase seemed inducible involving de novo protein synthesis.