title: Differences in the metal ion structure between Sr- and Ca-prothrombin fragment 1.
abstract: The structure of Sr-prothrombin fragment 1 has been solved and refined by restrained least-squares methods at 2.5-A resolution to a crystallographic R value of 0.167. The protein structure is very similar to that of Ca-fragment 1. A polymeric array of five Sr2+ ions separated by about 4.0 A is buried among six gamma-carboxyglutamic acid (Gla) residues; three other Sr2+ ions interact with other Gla residues and are located further apart. One of these was not found in the Ca-fragment 1 structure. The coordination of the Sr2+ ions resembles that of Ca2+, but there are some significant differences between them. The most notable is the lack of water coordination with Sr2+ ions and two conformations for Gla 8, which change the coordination of Sr-2 and Sr-3. A hexose moiety of an oligosaccharide was located in the vicinity of Asn101 that was flexibly disordered in Ca-fragment 1. The new Sr2+ ion found may be involved in metal ion phospholipid binding interactions along with Sr-1, and Sr-7, Sr-8.
authors.affiliation: Department of Chemistry, Michigan State University, East Lansing 48824.
authors.forename: T P
authors.initials: TP
authors.lastname: Seshadri
authors.forename: E
authors.initials: E
authors.lastname: Skrzypczak-Jankun
authors.forename: M
authors.initials: M
authors.lastname: Yin
authors.forename: A
authors.initials: A
authors.lastname: Tulinsky
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000737:chemistry*; D002417:Cattle; D008670:Metals / Q000737:chemistry*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D017510:Protein Folding; D011516:Prothrombin / Q000737:chemistry*; D013324:Strontium / Q000737:chemistry*
chemical_list: D008670:Metals; D010446:Peptide Fragments; D011516:Prothrombin; D002118:Calcium; D013324:Strontium