PDBsum entry 1cou

Blood clotting

PDB id: 1cou

Contents

Protein chain

85 a.a. *

* Residue conservation analysis

PDB id:

1cou

Name:

Blood clotting

Title:

Anticoagulant protein from the nematode ancylostoma caninum

Structure:

Protein (nematode anticoagulant protein c2). Chain: a. Synonym: napc2. Engineered: yes

Source:

Ancylostoma caninum. Dog hookworm. Organism_taxid: 29170. Expressed in: pichia pastoris. Expression_system_taxid: 4922.

NMR struc:

18 models

Authors:

B.M.Duggan,H.J.Dyson,P.E.Wright

Key ref:

B.M.Duggan et al. (1999). Inherent flexibility in a potent inhibitor of blood coagulation, recombinant nematode anticoagulant protein c2. Eur J Biochem, 265, 539-548. PubMed id: 10504384 DOI: 10.1046/j.1432-1327.1999.00781.x

Date:

28-May-99 Release date: 20-Oct-99

Protein chain

Q16938  (Q16938_ANCCA) -  Anti-coagulant protein C2 (Fragment) from Ancylostoma caninum

Seq: 91 a.a.

Struc: 85 a.a.

DOI no: 10.1046/j.1432-1327.1999.00781.x

Eur J Biochem 265:539-548 (1999)

PubMed id: 10504384

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

B.M.Duggan, H.J.Dyson, P.E.Wright.

ABSTRACT

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 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 VIIa 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 Halpha secondary shifts and 3JHNHalpha 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.

Selected figure(s)

Figure 7.
Fig. 7. ^15N-[^1H] heteronuclear NOEs of NAPc2. Heteronuclear NOEs were measured in triplicate. The pulse sequence of Farrow et al. [20] was used. Shaded bars identify the cysteine residues. The missing bars correspond to the prolines (P37, P40, P80 and P85) and the residues for which amide resonances were not observed (K1, K25 and H47).

Figure 10.
Fig. 10. Correlation of ^15N-[^1H] heteronuclear NOE and rmsd. See text for explanation. The diameter of the tube represents the rmsd of the backbone atoms. The tube is colored according to the heteronuclear NOE as follows: purple, NOE 0.8; blue, 0.8 > NOE 0.6; cyan 0.6 > NOE 0.4; yellow, 0.4 > NOE 0.2; orange, 0.2 > NOE 0.0; red, 0.0 > NOE. Residues K25, P37, P40, H47 and P80 are gray. Residues K1 and P85 are omitted for clarity. The cysteine side chains are shown as gold sticks. The protein is shown in the same orientation as the top left molecule of Fig. 9 Go-. This figure was prepared using MOLMOL [44].

The above figures are reprinted by permission from the Federation of European Biochemical Societies: Eur J Biochem (1999, 265, 539-548) copyright 1999.

Figures were selected by an automated process.