title: The role of tryptophan in staphylococcal nuclease stability.
abstract: Staphylococcal nuclease (SNase) has a single Trp residue at position 140. Circular dichroism, intrinsic and ANS-binding fluorescence, chemical titrations and enzymatic assays were used to measure the changes of its structure, stability and activities as the Trp was mutated or replaced to other positions. The results show that W140 is critical to SNase structure, stability, and function. Mutants such as W140A, F61W/W140A, and Y93W/W140A have unfolding, corrupted secondary and tertiary structures, diminished structural stability and attenuated catalytic activity as compared to the wild type. The deleterious effects of W140 substitution cannot be compensated by concurrent changes at topographical locations of position 61 or 93. Local hydrophobicity defined as a sum of hydrophobicity around a given residue within a distance is found to be a relevant property to SNase folding and stability.
authors.affiliation: Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan.
authors.forename: Hong-Yu
authors.initials: HY
authors.lastname: Hu
authors.forename: Ming-Chya
authors.initials: MC
authors.lastname: Wu
authors.forename: Huey-Jen
authors.initials: HJ
authors.lastname: Fang
authors.forename: Michael D
authors.initials: MD
authors.lastname: Forrest
authors.forename: Chin-Kun
authors.initials: CK
authors.lastname: Hu
authors.forename: Tian Yow
authors.initials: TY
authors.lastname: Tsong
authors.forename: Hueih Min
authors.initials: HM
authors.lastname: Chen
mesh_terms: D000817:Anilino Naphthalenesulfonates / Q000378:metabolism; D001974:Bromosuccinimide / Q000378:metabolism; D002942:Circular Dichroism; D004795:Enzyme Stability; D019791:Guanidine / Q000494:pharmacology; D008836:Micrococcal Nuclease / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011487:Protein Conformation; D058767:Protein Unfolding / Q000187:drug effects; D013050:Spectrometry, Fluorescence; D014270:Trifluoroethanol / Q000378:metabolism; D014364:Tryptophan
chemical_list: C515594:8-anilino-1-naphthalenesulfonic acid; D000817:Anilino Naphthalenesulfonates; D014270:Trifluoroethanol; D014364:Tryptophan; D008836:Micrococcal Nuclease; D019791:Guanidine; D001974:Bromosuccinimide