Inherent flexibility in a potent inhibitor of blood coagulation, recombinant nematode anticoagulant protein c2

被引:42
作者
Duggan, BM
Dyson, HJ
Wright, PE
机构
[1] Scripps Res Inst, Dept Mol Biol, La Jolla, CA 92037 USA
[2] Scripps Res Inst, Skaggs Inst Chem Biol, La Jolla, CA 92037 USA
来源
EUROPEAN JOURNAL OF BIOCHEMISTRY | 1999年 / 265卷 / 02期
关键词
blood coagulation; factor X; inhibitor; NMR; tissue factor;
D O I
10.1046/j.1432-1327.1999.00781.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Nematode anticoagulant proteins (NAPs) from the hematophagous nematode Ancylostoma caninum inhibit blood coagulation with picomolar inhibition constants, and have been targeted as novel pharmaceutical agents. NAPS and NAP6 inhibit factor Xa by binding to its active site, whereas NAPc2 binds to factor Xa at a different, as yet unidentified, site and the resultant binary complex inhibits the tissue factor-factor Wa complex. We have undertaken NMR studies of NAPc2, including the calculation of a solution structure, and found that the protein is folded, with five disulfide bonds, but is extremely flexible, especially in the acidic loop. The Ha secondary shifts and (3)J(HNH alpha) coupling constants indicate the presence of some beta structure and a short helix, but the intervening loops are highly conformationally heterogeneous. Heteronuclear NOE measurements showed the presence of large amplitude motions on a subnanosecond timescale at the N-terminus and C-terminus and in the substrate-binding loop, indicating that the conformational heterogeneity observed in the NMR structures is due to flexibility of the polypeptide chain in these regions. Flexibility may well be an important factor in the physiological function of NAPc2, because it must interact with other proteins in the inhibition of blood coagulation. We suggest that this inhibitor is likely to become structured on binding to factor Xa, because the inhibition of the tissue factor-factor VIIa complex requires both NAPc2 and factor Xa.
引用
收藏
页码:539 / 548
页数:10
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