PHOTOTRANSFORMATION AND PROTON-PUMPING ACTIVITY OF THE 14-FLUORO BACTERIORHODOPSIN DERIVATIVES

The photoinduced behavior and proton pumping characteristics of some b acteriorhodopsin (BR) analogs with fluorinated chromophores (all-trans 14-fluorinated [14-F] retinal and 13-cis 14-F retinal) derived from w ild type (WT) and D96N mutant BR were investigated. These analogs were characterized using spectrophotometry and a highly sensitive electroc hemical technique. Similar to the white membrane JW2N, the apomembrane s WT ET 1000 and D96N form photoactive pigments with the 14-F chromoph ores. The resulting analogs have a major absorption band at 588 nm, Re d-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 i n 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 analo gs derived from WT ET 1000, The measurements of the photoinduced trans formation in 14-F WT analogs show that the photocycle of the major pig ment occurs simultaneously with the process in the red region and is p artially masked by the formation of the red-shifted species. The 14-F D96N samples have a significantly slower and more complicated photoind uced behavior. Electrochemical measurements show that the photoinduced transformation of the red species is not accompanied by proton transp ort. (C) 1998 Elsevier Science B.V. All rights reserved.