Resonance energy transfer between cysteine-34, tryptophan-214, and tyrosine-411 of human serum albumin.

Reaction of p-nitrophenyl anthranilate with human serum albumin at pH 8.0 results in esterification of a single anthraniloyl moiety with the hydroxyl group of tyrosine-411. The absorption spectrum of the anthraniloyl group overlaps the fluorescence emission of the single tryptophan residue at position 214. This study complements that of the preceding paper [Suzukida, M., Le, H. P., Shahid, F., McPherson, R. A., Birnbaum, E.R., & Darnall, D. W. (1983) Biochemistry (preceding paper in this issue)] where an azomercurial group was introduced at cysteine-34. Anthraniloyl fluorescence was also quenched by the azomercurial absorption at Cys-34. Thus measurement of resonance energy transfer between these three sites allowed distances to be measured between Cys-34 in domain I, Trp-214 in domain II, and Tyr-411 in domain III of human serum albumin. At pH 7.4 in 0.1 M phosphate the Trp-214 leads to Tyr-411, Tyr-411 leads to Cys-34, and Trp-214 leads to Cys-34 distances were found to be 25.2 +/- 0.6, 25.2 +/- 2.1, and 31.8 +/- 0.8 A, respectively.