The structure of human MRP8, a member of the S100 calcium-binding protein family, by MAD phasing at 1.9 A resolution.
The structure of human MRP8 in the calcium-bound form was determined at 1.9 A resolution by X-ray crystallography. The structure was initially solved by MAD phasing of an ytterbium-substituted crystal and was refined against data obtained from a Ca(2+)-bound crystal. The dimeric form of MRP8 was stabilized by hydrophobic interactions between mutually wrapped helices. There were two EF-hand motifs per monomer and each EF-hand bound one Ca(2+) with a different affinity [the affinity of the C-terminal EF-hand (EF-2) for Ca(2+) was stronger than that of the N-terminal EF-hand (EF-1)]. Furthermore, replacement with Yb(3+) occurred in the C-terminal EF-hand only, suggesting a more flexible nature for EF-2 than for EF-1. This, combined with previous observations that the helix in EF-2 (helix III) undergoes a large conformational change upon calcium binding, suggests that the C-terminal EF-hand (EF-2) plays a role as a trigger for Ca(2+)-induced conformational change.
Ishikawa
K
K
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
Nakagawa
A
A
Tanaka
I
I
Suzuki
M
M
Nishihira
J
J
D000595:Amino Acid Sequence; D000943:Antigens, Differentiation / Q000737:chemistry*; D002135:Calcium-Binding Proteins / Q000737:chemistry*; D040501:Calgranulin A; D003196:Computer Graphics; D018360:Crystallography, X-Ray / Q000379:methods; D019281:Dimerization; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014978:Xenon; D015018:Ytterbium
D000943:Antigens, Differentiation; D002135:Calcium-Binding Proteins; D040501:Calgranulin A; D014978:Xenon; D015018:Ytterbium