Аннотация:The role of a conservative amino acid residue of tyrosine in the active center of retinal-containing proteins (Y185 in bacteriorhodopsin) in the regulation of the initial stages of the microbial rhodopsins photocycle is discussed. It is shown that the replace-ment of this residue leads to a significant change in the spectral-kinetic characteristics — a blue shift occurs in the wavelengths ofthe absorption maximum of the ground state, as well as the pri-mary intermediates I, J, and K by 10–15 nm. This shift is accom-panied by a more rapid decay of the excited state (intermediate I) and its transition to the main electronic level (intermediate J).The calculation of the electronic structure of the retinal and the nearest amino acid residues shows that these effects can be associated with electronic conjugation between the chromophore (retinal covalently associated with K216) and the aromatic residues Y185, W86 and W182.