PDBsum entry 4e05

Hydrolase/hydrolase inhibitor

PDB id: 4e05

Contents

Protein chains

29 a.a.

253 a.a.

30 a.a.

Ligands

NAG

Metals

_NA

Waters ×87

PDB id:

4e05

Name:

Hydrolase/hydrolase inhibitor

Title:

Anophelin from the malaria vector inhibits thrombin through a novel reverse-binding mechanism

Structure:

Thrombin. Chain: l. Fragment: light chain (unp residues 328-363). Synonym: coagulation factor ii. Thrombin. Chain: h. Fragment: heavy chain (unp residues 364-622). Synonym: coagulation factor ii. Salivary anti-thrombin peptide anophelin.

Source:

Homo sapiens. Human. Organism_taxid: 9606. Anopheles albimanus. New world malaria mosquito. Organism_taxid: 7167. Gene: anophelin. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.30Å R-factor: 0.171 R-free: 0.201

Authors:

A.C.Figueiredo,D.De Sanctis,R.Gutierrez-Gallego,T.B.Cereija,S.Macedo- Ribeiro,P.Fuentes-Prior,P.J.B.Pereira

Key ref:

A.C.Figueiredo et al. (2012). Unique thrombin inhibition mechanism by anophelin, an anticoagulant from the malaria vector. Proc Natl Acad Sci U S A, 109, E3649. PubMed id: 23223529

Date:

02-Mar-12 Release date: 05-Dec-12

Protein chain

P00734  (THRB_HUMAN) -  Prothrombin from Homo sapiens

Seq: 622 a.a.

Struc: 29 a.a.

Protein chain

P00734  (THRB_HUMAN) -  Prothrombin from Homo sapiens

Seq: 622 a.a.

Struc: 253 a.a.

Protein chain

Q9NJS1  (Q9NJS1_ANOAL) -  Salivary thrombin inhibitor anophelin from Anopheles albimanus

Seq: 83 a.a.

Struc: 30 a.a.

Enzyme reactions

• Enzyme class: Chains L, H: E.C.3.4.21.5 - thrombin.
• Reaction: Preferential cleavage: Arg-|-Gly; activates fibrinogen to fibrin and releases fibrinopeptide A and B.

Proc Natl Acad Sci U S A 109:E3649 (2012)

PubMed id: 23223529

Unique thrombin inhibition mechanism by anophelin, an anticoagulant from the malaria vector.

A.C.Figueiredo, D.de Sanctis, R.Gutiérrez-Gallego, T.B.Cereija, S.Macedo-Ribeiro, P.Fuentes-Prior, P.J.Pereira.

ABSTRACT

Anopheles mosquitoes are vectors of malaria, a potentially fatal blood disease affecting half a billion humans worldwide. These blood-feeding insects include in their antihemostatic arsenal a potent thrombin inhibitor, the flexible and cysteine-less anophelin. Here, we present a thorough structure-and-function analysis of thrombin inhibition by anophelin, including the 2.3-Å crystal structure of the human thrombin·anophelin complex. Anophelin residues 32-61 are well-defined by electron density, completely occupying the long cleft between the active site and exosite I. However, in striking contrast to substrates, the D50-R53 anophelin tetrapeptide occupies the active site cleft of the enzyme, whereas the upstream residues A35-P45 shield the regulatory exosite I, defining a unique reverse-binding mode of an inhibitor to the target proteinase. The extensive interactions established, the disruption of thrombin's active site charge-relay system, and the insertion of residue R53 into the proteinase S(1) pocket in an orientation opposed to productive substrates explain anophelin's remarkable specificity and resistance to proteolysis by thrombin. Complementary biophysical and functional characterization of point mutants and truncated versions of anophelin unambiguously establish the molecular mechanism of action of this family of serine proteinase inhibitors (I77). These findings have implications for the design of novel antithrombotics.