TIME-RESOLVED FLUORESCENCE STUDIES ON SITE-DIRECTED MUTANTS OF HUMAN SERUM-ALBUMIN

Human serum albumin (HSA) contains a single tryptophan residue at posi tion 214. The emission properties of tryptophan 214 from recombinant a lbumins, namely, normal HSA, FDH-HSA and a methionine 218 HSA were exa mined. In all cases, the excited state lifetimes mere best described b y a two component model consisting mainly of a Lorentzian distribution . The centers of these distributions were 5.60 ns for HSA, 4.23 ns for FDH-HSA, and 6.08 ns for Met-218 HSA. The global rotational correlati on times of the three HSAs were near 41 ns while the amplitude and rat e of the local motion varied. These changes in the lifetimes and mobil ities suggest perturbation in the local protein environment near trypt ophan 214 as a consequence of the amino acid substitutions. (C) 1997 F ederation of European Biochemical Societies.