4E05

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

Summary for 4E05

• Entry DOI: 10.2210/pdb4e05/pdb
• Related: 4E06
• Descriptor: Thrombin, Salivary anti-thrombin peptide anophelin, 2-acetamido-2-deoxy-beta-D-glucopyranose, ... (6 entities in total)
• Functional Keywords: hydrolase-hydrolase inhibitor complex, hydrolase/hydrolase inhibitor
• Biological source: Anopheles albimanus (New world malaria mosquito); More
• Total number of polymer chains: 3
• Total formula weight: 40663.65

Authors

Figueiredo, A.C.,de Sanctis, D.,Gutierrez-Gallego, R.,Cereija, T.B.,Macedo-Ribeiro, S.,Fuentes-Prior, P.,Pereira, P.J.B. (deposition date: 2012-03-02, release date: 2012-12-05, Last modification date: 2024-11-06)

Primary citation

Figueiredo, A.C.,de Sanctis, D.,Gutierrez-Gallego, R.,Cereija, T.B.,Macedo-Ribeiro, S.,Fuentes-Prior, P.,Pereira, P.J.
Unique thrombin inhibition mechanism by anophelin, an anticoagulant from the malaria vector.
Proc.Natl.Acad.Sci.USA, 109:E3649-E3658, 2012

PubMed 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.

PubMed: 23223529
DOI: 10.1073/pnas.1211614109

Experimental method

X-RAY DIFFRACTION (2.304 Å)