title: Refined crystal structure of ytterbium-substituted carp parvalbumin 4.25 at 1.5 A, and its comparison with the native and cadmium-substituted structures.
abstract: The crystal structure of carp parvalbumin 4.25 containing a 1:1 molar ratio of ytterbium chloride to protein has been refined at 1.5 A resolution by restrained least-squares methods to a crystallographic R value of 0.199. The crystal structure confirms the NMR studies, which suggest that low concentrations of ytterbium cause an extensive displacement of calcium from the EF metal binding site. A comparison of the ytterbium-substituted model with the native and cadmium-substituted structure show no significant differences, except around the substituted EF metal-binding region. The displacement of calcium by ytterbium at the EF site has caused a movement in the polypeptide backbone of Ser-91 and Asp-92. This movement resulted in an increase in the number of oxygen ligands bound to ytterbium in the EF site from seven to eight.
authors.affiliation: Macromolecular Structure Laboratory, NCI-Frederick Cancer Research and Development Center, MD 21702-1201.
authors.forename: V D
authors.initials: VD
authors.lastname: Kumar
authors.forename: L
authors.initials: L
authors.lastname: Lee
authors.forename: B F
authors.initials: BF
authors.lastname: Edwards
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002104:Cadmium / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002347:Carps; D008958:Models, Molecular; D010320:Parvalbumins / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D011487:Protein Conformation / Q000187:drug effects; D014961:X-Ray Diffraction / Q000379:methods; D015018:Ytterbium / Q000494:pharmacology*
chemical_list: D010320:Parvalbumins; D002104:Cadmium; D015018:Ytterbium; D002118:Calcium