PDBsum entry 2pc4

Lyase

PDB id: 2pc4

Contents

Protein chains

359 a.a.

Ligands

ASP-TRP-ASN

Waters ×519

References listed in PDB file

Key reference

Title

Aldolase provides an unusual binding site for thrombospondin-Related anonymous protein in the invasion machinery of the malaria parasite.

Authors

J.Bosch, C.A.Buscaglia, B.Krumm, B.P.Ingason, R.Lucas, C.Roach, T.Cardozo, V.Nussenzweig, W.G.Hol.

Ref.

Proc Natl Acad Sci U S A, 2007, 104, 7015-7020. [DOI no: 10.1073/pnas.0605301104]

PubMed id

17426153

Abstract

An actomyosin motor located underneath the plasma membrane drives motility and host-cell invasion of apicomplexan parasites such as Plasmodium falciparum and Plasmodium vivax, the causative agents of malaria. Aldolase connects the motor actin filaments to transmembrane adhesive proteins of the thrombospondin-related anonymous protein (TRAP) family and transduces the motor force across the parasite surface. The TRAP-aldolase interaction is a distinctive and critical trait of host hepatocyte invasion by Plasmodium sporozoites, with a likely similar interaction crucial for erythrocyte invasion by merozoites. Here, we describe 2.4-A and 2.7-A structures of P. falciparum aldolase (PfAldo) obtained from crystals grown in the presence of the C-terminal hexapeptide of TRAP from Plasmodium berghei. The indole ring of the critical penultimate Trp-residue of TRAP fits snugly into a newly formed hydrophobic pocket, which is exclusively delimited by hydrophilic residues: two arginines, one glutamate, and one glutamine. Comparison with the unliganded PfAldo structure shows that the two arginines adopt new side-chain rotamers, whereas a 25-residue subdomain, forming a helix-loop-helix unit, shifts upon binding the TRAP-tail. The structural data are in agreement with decreased TRAP binding after mutagenesis of PfAldo residues in and near the induced TRAP-binding pocket. Remarkably, the TRAP- and actin-binding sites of PfAldo seem to overlap, suggesting that both the plasticity of the aldolase active-site region and the multimeric nature of the enzyme are crucial for its intriguing nonenzymatic function in the invasion machinery of the malaria parasite.

Figure 2.
Fig. 2. Key interactions of the TRAP-tail with P. falciparum aldolase. (A) TRAP-tail residues D604, W605, and N606 (magenta) interacting with PfAldo residues (light blue). C[ ]positions are marked as spheres. Selected hydrophobic contacts are shown with red lines and distances in angstroms. The hydrogen bond between the indole nitrogen of TRAP-W605 and the carboxylate of E40, and the interactions between TRAP-N606 with R153 and K151, and of the backbone oxygen of TRAP-D604 with R48, are depicted in black. (B) Sequence alignment of the C-terminal TRAP-tail residues of three plasmodial species. Identical residues are shaded in red. All TRAP residues involved in contacts with aldolase are well conserved in several Plasmodium species.

Figure 4.
Fig. 4. TRAP-tail binding interferes with substrate binding. Shown is a stereoview of the PfAldo:TRAP-tail complex superimposed onto the structure of human aldolase A complexed with F1,6P (30) (PDB ID code 4ALD). Key residues enabling the accommodation of the penultimate Trp-indole ring are highlighted as sticks. The TRAP-tail is shown in magenta, residues involved in substrate binding in blue, and human aldolase A in yellow. The substrate F1,6P are shown as sticks in green, with the two phosphate groups in orange. The C-terminal TRAP-tail residue partially occludes the substrate-binding site.