Cra and the control of carbon flux via metabolic pathways.

The catabolite repressor-activator (Cra) protein controls the direction of carbon flux through metabolic pathways in enteric bacteria. Cra binds to the control regions of target genes and exerts a negative effect on the expression of genes encoding glycolytic and Entner-Doudoroff enzymes, while exerting a positive effect on genes encoding Krebs cycle, glyoxylate shunt and gluconeogenic enzymes. Cra mediates cyclic AMP-independent catabolite repression of positively Cra-regulated genes and catabolite activation of negatively Cra-controlled genes.