Carrier-mediated glutamate secretion by Corynebacterium glutamicum under biotin limitation.

Previous studies have demonstrated the involvement of a carrier system in glutamate secretion by Corynebacterium glutamicum under biotin limitation (Hoischen, C. and Krämer, R. (1989) Arch. Microbiol. 151, 342-347). In a detailed analysis of the export process we found secretion to be independent of secondary forces: (i) glutamate was secreted at high rate even when external glutamate exceeded the internal concentration, (ii) movement of neither protons nor potassium or chloride ions was found to be coupled to glutamate secretion, and (iii) secretion continued unaffected after breakdown of the membrane potential. Instead, under conditions leading to variation of glutamate secretion activity, a correlation of secretion rate and the intracellular ATP-pool was observed. Thus, ATP or a related high-energy metabolite is thought to be involved in the activity of the glutamate secretion system.