Shape change in the receptor for gliding motility in Plasmodium sporozoites

Abstract

Sporozoite gliding motility and invasion of mosquito and vertebrate host cells in malaria is mediated by thrombospondin repeat anonymous protein (TRAP). Tandem von Willebrand factor A (VWA) and thrombospondin type I repeat (TSR) domains in TRAP connect through proline-rich stalk, transmembrane, and cytoplasmic domains to the parasite actin-dependent motility apparatus. We crystallized fragments containing the VWA and TSR domains from Plasmodium vivax and Plasmodium falciparum in different crystal lattices. TRAP VWA domains adopt closed and open conformations, and bind a Mg 2+ ion at a metal ion-dependent adhesion site implicated in ligand binding. Metal ion coordination in the open state is identical to that seen in the open high-affinity state of integrin I domains. The closed VWA conformation associates with a disordered TSR domain. In contrast, the open VWA conformation crystallizes with an extensible β ribbon and ordered TSR domain. The extensible β ribbon is composed of disulfide-bonded segments N-and C-terminal to the VWA domain that are largely drawn out of the closed VWA domain in a 15 Å movement to the open conformation. The extensible β ribbon and TSR domain overlap at a conserved interface. The VWA, extensible β ribbon, and TSR domains adopt a highly elongated overall orientation that would be stabilized by tensile force exerted across a ligand-receptor complex by the actin motility apparatus of the sporozoite. Our results provide insights into regulation of "stick-and-slip" parasite motility and for development of sporozoite subunit vaccines. M osquitoes transmit malaria to humans via sporozoites. Sporozoites are important targets of pre-erythrocytic malaria vaccines. However, we know little about the structure and arrangement of the two most important vaccine targets on sporozoite surfaces, the circumsporozoite (CS) protein (1-3) and thrombospondin repeat anonymous protein (TRAP) (4, 5). CS is a constitutive sporozoite surface protein and has a glycophosphatidylinositol anchor. TRAP mediates sporozoite gliding motility and cell invasion in both mosquito and vertebrate hosts (6).TRAP is mobilized from micronemes to the plasma membrane at the apical end of sporozoites, and is translocated to the posterior end during cell migration and invasion (7,8). TRAP spans the plasma membrane, and its cytoplasmic domain connects to the actin cytoskeleton through aldolase, permitting functional cooperation between extracellular adhesive domains and the intracellular actin/myosin motor (8-10). The TRAP ectodomain contains tandem von Willebrand factor A (VWA) and thrombospondin repeat (TSR) domains. A subset of VWA domains, including the inserted (I) domains in integrins, contain metal ion-dependent adhesion sites (MIDAS), with a Mg 2+ ion at the center of the ligand binding site (11). Conformational change transmitted from neighboring domains regulates affinity of I domains for ligand. The TRAP VWA domain contains the sequence signature of a MIDAS. Mutations of putative TRAP VWA domain MIDAS residues and deletion o...

Structural and functional features of a collagen-binding matrix protein from the mussel byssus

“…In addition, the binding differs to that of von Willebrand factor since PTMP1 lacks nearly all of the critical interacting residues of the vWFA3 domain 12 . In the von Willebrand factor and other VWA domain proteins, C-terminal helix and linker act as a switch region between an open and a closed state with low and high affinity for metal and ligand 33 . Interestingly, the C termini of A1 and A2 are coupled in PTMP1, suggesting that a mechanism regulating their ligand affinity could affect both domains concomitantly.…”

Structural Basis of Regulation of von Willebrand Factor Binding to Glycoprotein Ib

“…The presence of long range disulfide bonds does not prevent conformational change in VWA domains, as illustrated by the 15-Å movement of the long range disulfide in the VWA domain of a sporozoite adhesin (41). In integrin I domains, a force exerted in a similar C-terminal direction on the C-terminal ␣-helix induces axial pistoning of this helix that leads to a large increase in affinity for ligand (11).…”

Biosynthesis of GDP-fucose and Other Sugar Nucleotides in the Blood Stages of Plasmodium falciparum

“…TSR domains are generally O-fucosylated in higher eukaryotes by PoFUT2, and the fucose residue can be further modified by the addition of ␤1-3 glucose (72-74). The C-terminal region of CS, containing the TSR domain, was recently expressed in HEK293T cells and structurally analyzed, showing the presence of a fucose and a glucose residue (75,76). The expression of PoFUT2 in P. falciparum (Fig.…”