Figure 1.

Working model for pathway for bacterial lipoic acid metabolism and its possible regulation. (A) A pathway proposed for lipoic acid synthesis and its scavenging in Shewanella. LipA, lipoic acid synthase; LipB, Octanoyl-ACP: protein ligase (N-octanoyltransferase); PdhR, pyruvate dehydrogenase operon repressor; LD, lipoyl domain (in light blue); ACP, acyl carrier protein (in white oval). Shewanella lipB/A expression is shut off by the cAMP-CRP complex on the condition of low glucose level (or high cAMP concentration) (B), whereas is induced upon high concentration of glucose is available (or cytosolic cAMP is limited) (C). Blue dots denote cAMP molecules, green regular hexagon represents glucose, and purple ovals indicate CRP protein. CRP, cAMP-receptor protein.