4TPV: Crystal Structure Of Hookworm Platelet Inhibitor

Citation:
Abstract
Secreted protein components of hookworm species include a number of representatives of the cysteine-rich/antigen 5/pathogenesis-related 1 (CAP) protein family known as Ancylostoma-secreted proteins (ASPs). Some of these have been considered as candidate antigens for the development of vaccines against hookworms. The functions of most CAP superfamily members are poorly understood, but one form, the hookworm platelet inhibitor (HPI), has been isolated as a putative antagonist of the platelet integrins alphaIIbbeta3 and alpha2beta1. Here, the crystal structure of HPI is described and its structural features are examined in relation to its possible function. The HPI structure is similar to those of other ASPs and shows incomplete conservation of the sequence motifs CAP1 and CAP2 that are considered to be diagnostic of CAP superfamily members. The asymmetric unit of the HPI crystal contains a dimer with an extensive interaction interface, but chromatographic measurements indicate that it is primarily monomeric in solution. In the dimeric structure, the putative active-site cleft areas from both monomers are united into a single negatively charged depression. A potential Lys-Gly-Asp disintegrin-like motif was identified in the sequence of HPI, but is not positioned at the apex of a tight turn, making it unlikely that it interacts with the integrin. Recombinant HPI produced in Escherichia coli was found not to inhibit the adhesion of human platelets to collagen or fibrinogen, despite having a native structure as shown by X-ray diffraction. This result corroborates previous analyses of recombinant HPI and suggests that it might require post-translational modification or have a different biological function.
PDB ID: 4TPVDownload
MMDB ID: 128741
PDB Deposition Date: 2014/6/9
Updated in MMDB: 2015/06
Experimental Method:
x-ray diffraction
Resolution: 1.6  Å
Source Organism:
Similar Structures:
Biological Unit for 4TPV: monomeric; determined by author
Molecular Components in 4TPV
Label Count Molecule
Protein (1 molecule)
1
Platelet Inhibitor
Molecule annotation
Chemical (1 molecule)
1
1
* Click molecule labels to explore molecular sequence information.

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