Biochemical characterization of two Azotobacter vinelandii FKBPs and analysis of their interaction with the small subunit of carbamoyl phosphate synthetase

Functional interaction of Azotobacter vinelandii cytoplasmic cyclophilin with the biotin carboxylase subunit of acetyl-CoA carboxylase

Cyclophilins (E.C. 5.1.2.8) are protein chaperones with peptidyl-prolyl cis/trans isomerase activity (PPIase). In the present study, we demonstrate a physical interaction among AvppiB, encoding the cytoplasmic cyclophilin from the soil nitrogen-fixing bacterium Azotobacter vinelandii, and AvaccC, encoding the biotin carboxylase subunit of acetyl-CoA carboxylase, which catalyzes the committed step in long-chain fatty acid synthesis. A decrease in AvppiB PPIase activity, in the presence of AvaccC, further confirms the interaction. However, PPIase activity seems not to be essential for these interactions since a PPIase active site mutant of cyclophilin does not abolish the AvaccC binding. We further show that the presence of cyclophilin largely influences the measured ATP hydrolyzing activity of AvaccA in a way that is negatively regulated by the PPIase activity. Taken together, our data support a novel role for cyclophilin in regulating biotin carboxylase activity.