Structural reorganization of the copper binding site involving Thr15 of mavicyanin from Cucurbita pepo medullosa (zucchini) upon reduction.
Mavicyanin, a glycosylated protein isolated from Cucurbita pepo medullosa (zucchini), is a member of the phytocyanin subfamily containing one polypeptide chain of 109 amino residues and an unusual type-I Cu site in which the copper ligands are His45, Cys86, His91, and Gln96. The crystal structures of oxidized and reduced mavicyanin were determined at 1.6 and 1.9 A resolution, respectively. Mavicyanin has a core structure of seven polypeptide beta-strands arranged as a beta-sandwich organized into two beta-sheets, and the structure considerably resembles that of stellacyanin from cucumber (CST) or cucumber basic protein (CBP). A flexible region was not observed on superimpositioning of the oxidized and reduced mavicyanin structures. However, the Cu(II)-epsilon-O-Gln96 bond length was extended by 0.47 A, and the Thr15 residue was rotated by 60.0 degrees and O-gamma1-Thr15 moved from a distance of 4.78 to 2.58 A from the ligand Gln96 forming a new hydrogen bond between O-gamma1-Thr15 and epsilon-O-Gln96 upon reduction. The reorganization of copper coordination geometry of mavicyanin upon reduction arouses reduction potential decreased above pH 8 [Battistuzzi et al. (2001) J. Inorg. Biochem. 83, 223-227]. The rotation of Thr15 and the hydrogen bonding with the ligand Gln96 may constitute structural evidence of the decrease in the reduction potential at high pH.
Xie
Yong
Y
Department of Materials Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871.
Inoue
Tsuyoshi
T
Miyamoto
Yoichi
Y
Matsumura
Hiroyoshi
H
Kataoka
Kunishige
K
Yamaguchi
Kazuya
K
Nojini
Masaki
M
Suzuki
Shinnichiro
S
Kai
Yasushi
Y
D000595:Amino Acid Sequence; D001665:Binding Sites / Q000187:drug effects; D003300:Copper / Q000378:metabolism*; D008667:Metalloproteins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000737:chemistry*; D013912:Threonine / Q000737:chemistry*; D014961:X-Ray Diffraction
D008667:Metalloproteins; D010940:Plant Proteins; C022828:mavicyanin protein, Cucurbita pepo; C003343:stellacyanin protein, plant; C072144:CBP protein, Cucumis sativus; D013912:Threonine; D003300:Copper