EPR mapping of interactions between spin-labeled variants of human carbonic anhydrase II and GroEL: evidence for increased flexibility of the hydrophobic core by the interaction

Human carbonic anhydrase II (HCA II) interacts weakly with GroEL at room temperature. Electron paramagnetic resonance (EPR) spectroscopy was employed to investigate HCA II cysteine mutants spin-labeled at selected positions to further study the interaction. Findings showed that protein-protein interactions can be specifically mapped by site-directed spin-labeling and EPR measurements. HCA II had to be unfolded to approximately the same extent as a GuHCl-induced molten-globule intermediate of the enzyme to interact with GroEL.