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

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. NAP5 NAP6 factor Xa by binding to its active site, whereas NAPc2 binds at a different, yet unidentified, site resultant binary complex inhibits tissue factor–factor VIIa complex. We undertaken NMR studies of NAPc2, including calculation solution structure, found that protein is folded, five disulfide bonds, but extremely flexible, especially in acidic loop. The Hα secondary shifts 3JHNHα coupling constants indicate presence some β structure short helix, intervening loops are highly conformationally heterogeneous. Heteronuclear NOE measurements showed large amplitude motions on subnanosecond timescale N-terminus C-terminus substrate-binding loop, indicating conformational heterogeneity observed structures due flexibility polypeptide chain these regions. Flexibility may well be an important physiological function because it must interact other coagulation. suggest this inhibitor likely become structured Xa, requires both Xa.