Evidence for light-induced lysine conformational changes during the primary event of the bacteriorhodopsin photocycle

Fourier transform infrared difference spectroscopy is used to examine the role of lysine in the primary event of the bacteriorhodopsin photocycle. Isotopically labeled lysine is used to tentatively assign the lysine modes in the BR and K species. The results suggest that the lysine side-chain undergoes conformational changes in concert with the known light-induced chromophore structural alterations.