1887

Abstract

Summary: Two temperature-sensitive mutants of 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 cytochrome . 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 C metabolism. Cosmid pAD833, which has previously been shown to carry genes involved in methanol oxidation ( 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 genes. This region was near an 8 kbp region containing the gene which complemented mutant NH-4.

Loading

Article metrics loading...

/content/journal/micro/10.1099/00221287-139-3-539
1993-03-01
2019-10-14
Loading full text...

Full text loading...

http://instance.metastore.ingenta.com/content/journal/micro/10.1099/00221287-139-3-539
Loading
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error