Interaction of the Nitrogen Regulatory Protein GlnB (P) with Biotin Carboxyl Carrier Protein (BCCP) Controls Acetyl-CoA Levels in the Cyanobacterium sp. PCC 6803.

The family of P signal transduction proteins (members GlnB, GlnK, NifI) plays key roles in various cellular processes related to nitrogen metabolism at different functional levels. Recent studies implied that P proteins may also be involved in the regulation of fatty acid metabolism, since GlnB proteins from Proteobacteria and from were shown to interact with biotin carboxyl carrier protein (BCCP) of acetyl-CoA carboxylase (ACC). In case of ACCase, this interaction reduces the k of acetyl-CoA carboxylation, which should have a marked impact on the acetyl-CoA metabolism. In this study we show that the P protein of a unicellular cyanobacterium inhibits the biosynthetic activity of ACC and also interacts with cyanobacterial BCCP in an ATP and 2-oxoglutarate dependent manner. In a P mutant strain of strain PCC 6803, the lacking control leads to reduced acetyl-CoA levels, slightly increased levels of fatty acids and formation of lipid bodies as well as an altered fatty acid composition.