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BIOSYNTHETIC INCORPORATION OF M‐FLUOROTYROSINE INTO BACTERIORHODOPSIN
Author(s) -
Hazard E. Starr,
Govindjee Rajni,
Ebrey Thomas G.,
Crouch Rosalie K.
Publication year - 1992
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1992.tb09715.x
Subject(s) - bacteriorhodopsin , chemistry , membrane , halobacterium , tyrosine , isoelectric focusing , halobacteriaceae , trifluoroacetic acid , chromatography , amino acid , kinetics , phenylalanine , biochemistry , halobacterium salinarum , enzyme , physics , quantum mechanics
—Halobacterium halobium , grown in a defined medium where tyrosine had been largely replaced with m‐fluorotyrosine, biosynthetically produced purple membrane. Analysis of this membrane by high pressure liquid chromatography of phenylthiocarbamyl derivatized amino acids of membrane acid hydrolysates revealed that up to 50% of the tyrosine was present as the m‐fluorotyrosine form. Yields of the purple membrane decreased as the level of incorporation increased. The experimental purple membrane showed a single 19 F NMR resonance at ‐61.983 ppm (relative to trifluoroacetic acid). The bacteriorhodopsin (bR) in the purple membrane was normal as assayed by gel electrophor‐esis, isoelectric focusing, circular dichroic spectra, and UV‐visible spectra. However, the fluorinated tyrosine bacteriorhodopsins at near neutral pH exhibited slightly slower rates of proton uptake and a slower M‐state decay with biphasic kinetics reminiscent of alkaline solutions of bR (pH > 9). These results imply that the tyrosines in bacteriorhodopsin may play a role in the photoactivated proton translocation process of this pigment.