title: Tryptophan mutants of human C5a anaphylatoxin: a fluorescence anisotropy decay and energy transfer study.
abstract: Three mutants of the anaphylatoxin C5a were prepared with positions 2, 64 and 70, respectively, substituted by tryptophan. The last mutant was additionally labelled at Cys27 for fluorescence energy transfer (FET) measurements. The structural integrity and biological activity of the molecules were not affected. Fluorescence anisotropy decay (FAD) measurements showed that the rotational correlation time for tryptophan decreases in the order: [Trp2]rhC5a > [Trp64]rhC5a > [Trp70]rhC5a, indicating an increasing mobility of the side chain. Measurements of the fluorescence energy transfer from Trp70 to the 1,5-AEDANS group at Cys27 yielded a distance distribution of 2.4 +/- 0.8 nm. This value is compatible with the C-terminal chain being arranged as a slightly stretched helix pointing away from the body of the molecule.
authors.affiliation: Institut für Biochemie, Rheinisch-Westfälische Technische Hochschule Aachen, Klinikum, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Federwisch
authors.forename: A
authors.initials: A
authors.lastname: Wollmer
authors.forename: M
authors.initials: M
authors.lastname: Emde
authors.forename: T
authors.initials: T
authors.lastname: Stühmer
authors.forename: T
authors.initials: T
authors.lastname: Melcher
authors.forename: A
authors.initials: A
authors.lastname: Klos
authors.forename: J
authors.initials: J
authors.lastname: Köhl
authors.forename: W
authors.initials: W
authors.lastname: Bautsch
mesh_terms: D000595:Amino Acid Sequence; D000706:Anaphylatoxins / Q000737:chemistry* / Q000235:genetics; D002942:Circular Dichroism; D015936:Complement C5a / Q000737:chemistry* / Q000235:genetics; D003545:Cysteine; D004735:Energy Transfer; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009282:Naphthalenesulfonates; D011994:Recombinant Proteins / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013439:Sulfhydryl Reagents; D013997:Time Factors; D014364:Tryptophan / Q000737:chemistry* / Q000235:genetics
chemical_list: D000706:Anaphylatoxins; D005456:Fluorescent Dyes; D009282:Naphthalenesulfonates; D011994:Recombinant Proteins; D013439:Sulfhydryl Reagents; C006421:1,5-I-AEDANS; D015936:Complement C5a; D014364:Tryptophan; D003545:Cysteine