Glutamine synthetases of Corynebacterium glutamicum: transcriptional control and regulation of activity

Regulation of glnA expression and glutamine synthetase I activity was analy zed in Corynebacterium glutamicum. Transcription is regulated by the global repressor protein AmtR, essential for derepression ol glnA transcription a re GlnK and uridylyltransferase, key proteins of the C. glutamicum nitrogen regulatory system. Glutamine synthetase I activity is controlled by adenyl ylation/deadenylylation via adenylyltransferase. The gene encoding this bif unctional enzyme, glnE, was isolated and its function was characterized by deletion analysis. Upstream of glnE, a second gene encoding a GSI-type prot ein in C. glutamicum was isolated. This gent, designated gln, 12, forms an operon with glnE, its transcription is not regulated and neither its deleti on or overexpression showed any effect. Therefore. the physiological role o f glnA2 remains unclear. (C) 2001 Federation of European Microbiological So cieties. Published by Elsevier Science B.V. All rights reserved.