Phototransformation and proton pumping activity of the 14-fluoro bacteriorhodopsin derivatives.

The photoinduced behavior and proton pumping characteristics of some bacteriorhodopsin (BR) analogs with fluorinated chromophores (all-trans 14-fluorinated [14-F] retinal and 13-cis 14-F retinal) derived from wild type (WT) and D96N mutant BR were investigated. These analogs were characterized using spectrophotometry and a highly sensitive electrochemical technique. Similar to the white membrane JW2N, the apomembranes WT ET 1000 and D96N form photoactive pigments with the 14-F chromophores. The resulting analogs have a major absorption band at 588 nm, Red-shifted pigment (lambda(max) less than or equal to 680 nm) has been previously observed as a minor component of the major 587-nm pigment in 14-F BR made with white membrane JW2N. A similar red-shifted pigment is formed under yellow light (lambda > 500 nm) only in the 14-F analogs derived from WT ET 1000, The measurements of the photoinduced transformation in 14-F WT analogs show that the photocycle of the major pigment occurs simultaneously with the process in the red region and is partially masked by the formation of the red-shifted species. The 14-F D96N samples have a significantly slower and more complicated photoinduced behavior. Electrochemical measurements show that the photoinduced transformation of the red species is not accompanied by proton transport. (C) 1998 Elsevier Science B.V. All rights reserved.