title: The contribution of metal ions to the conformational stability of ribonuclease T1: crystal versus solution.
abstract: In the crystalline state, ribonuclease T1 binds calcium ions at different lattice-dependent positions. In solution, its conformational stability is also remarkably increased in the presence of divalent metal ions. Combining urea unfolding studies and X-ray crystallography, we compared the presence of several metal ions at specific sites in the protein to their contribution to the overall stabilizing effect in solution. We constructed thermodynamic cycles involving particular metal ions and specific carboxylate functions. The resulting coupling energies indicate that some (but not all) metal ions found at lattice contacts in crystal structures may indeed significantly contribute to stability enhancement in the presence of metal ions in solution.
authors.affiliation: Laboratorium voor Ultrastructuur, Vlaams Interuniversitair Instituut voor Biotechnologie, Vrije Universiteit Brussel, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Deswarte
authors.forename: S
authors.initials: S
authors.lastname: De Vos
authors.forename: U
authors.initials: U
authors.lastname: Langhorst
authors.forename: J
authors.initials: J
authors.lastname: Steyaert
authors.forename: R
authors.initials: R
authors.lastname: Loris
mesh_terms: D001224:Aspartic Acid / Q000737:chemistry; D002413:Cations, Divalent; D018360:Crystallography, X-Ray; D004795:Enzyme Stability; D008274:Magnesium; D008670:Metals; D008672:Metals, Alkali; D008673:Metals, Alkaline Earth; D008956:Models, Chemical; D009154:Mutation; D011487:Protein Conformation; D011489:Protein Denaturation; D006163:Ribonuclease T1 / Q000737:chemistry* / Q000235:genetics; D013816:Thermodynamics; D014508:Urea / Q000494:pharmacology
chemical_list: D002413:Cations, Divalent; D008670:Metals; D008672:Metals, Alkali; D008673:Metals, Alkaline Earth; D001224:Aspartic Acid; D014508:Urea; D006163:Ribonuclease T1; D008274:Magnesium