@article{mbs:/content/journal/micro/10.1099/00221287-139-3-539, author = "Hutchinson, N. and Goodwin, P. M.", title = "Characterization and Complementation of Mutants of Methylophilus Methylotrophus that have Thermolabile Forms of Proteins Involved in C1 Metabolism", journal= "Microbiology", year = "1993", volume = "139", number = "3", pages = "539-546", doi = "https://doi.org/10.1099/00221287-139-3-539", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-139-3-539", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", abstract = "Two temperature-sensitive mutants of Methylophilus methylotrophus have been isolated and characterized. The first, NH-4, had a temperature-sensitive defect in methylamine oxidation and was unable to utilize methylamine as sole carbon and nitrogen source at 42 °C. The activities of the methylamine oxidation system and methylamine dehydrogenase in cells grown on methylamine at 30 °C were much more thermolabile than those of the wild-type. Furthermore, the affinity of the mutant enzyme for methylamine was lower than that of the wild-type enzyme. These results suggest that NH-4 produces a mutant enzyme with an altered conformation which is more susceptible to thermal denaturation than the wild-type enzyme. Surprisingly, this mutant could grow at 42 °C on media containing methylamine if an alternative carbon or nitrogen source was available. The methylamine oxidation system of whole cells grown under these conditions was not inactivated at 42 °C. The second mutant, NH-7, was unable to grow at the restrictive temperature on media containing either methanol or methylamine as sole carbon source. It contained thermolabile forms of methanol and methylamine dehydrogenases and cytochrom c L. This phenotype could be due to a mutation in a gene essential for the production of mature forms of these periplasmic proteins, which are involved in C1 metabolism. Cosmid pAD833, which has previously been shown to carry genes involved in methanol oxidation (mox genes), complemented both NH-4 and NH-7. Subcloning indicated that the gene which complemented NH-7 was within a 3 kbp region which contained at least two mox genes. This region was near an 8 kbp region containing the gene which complemented mutant NH-4.", }