Gruszczyk, JakubLim, Nicholas T.Y.Arnott, AliciaHe, Wen QiangNguitragool, WangRoobsoong, WanlapaMok, Yee FoongMurphy, James M.Smith, Katherine R.Lee, StuartBahlo, MelanieMueller, IvoBarry, Alyssa E.Tham, Wai Hong2026-01-012026-01-010027-8424PubMed:26715754ORCID:/0000-0001-7950-8699/work/218987882https://hdl.handle.net/1885/733802063Understanding how malaria parasites gain entry into human red blood cells is essential for developing strategies to stop blood stage infection. Plasmodium vivax preferentially invades reticulocytes, which are immature red blood cells. The organism has two erythrocyte-binding protein families: namely, the Duffy-binding protein (PvDBP) and the reticulocyte-binding protein (PvRBP) families. Several members of the PvRBP family bind reticulocytes, specifically suggesting a role in mediating host cell selectivity of P. vivax. Here, we present, to our knowledge, the first high-resolution crystal structure of an erythrocyte-binding domain from PvRBP2a, solved at 2.12 Å resolution. The monomeric molecule consists of 10 α-helices and one short β-hairpin, and, although the structural fold is similar to that of PfRh5-the essential invasion ligand in Plasmodium falciparum-its surface properties are distinct and provide a possible mechanism for recognition of alternate receptors. Sequence alignments of the crystallized fragment of PvRBP2a with other PvRBPs highlight the conserved placement of disulfide bonds. PvRBP2a binds mature red blood cells through recognition of an erythrocyte receptor that is neuraminidase- and chymotrypsinresistant but trypsin-sensitive. By examining the patterns of sequence diversity within field isolates, we have identified and mapped polymorphic residues to the PvRBP2a structure. Using mutagenesis, we have also defined the critical residues required for erythrocyte binding. Characterization of the structural features that govern functional erythrocyte binding for the PvRBP family provides a framework for generating new tools that block P. vivax blood stage infection.We thank Janet Newman and Shane Seabrook from the CSIRO Collaborative Crystallization Centre (C3) for help with setting up the crystallization screens, the Walter and Eliza Hall Institute''s Monoclonal Antibody Facility for production of antibodies, and the MX and SAXS beamline staff at the Australian Synchrotron for assistance during data collection. We thank Prof. Mike Lawrence at the Walter and Eliza Hall Institute for critical comments on the manuscript. This work was supported by an Australian Research Council Future Fellowship (toW.-H.T.) and an NHMRC Senior Research Fellowship and NHMRC Program Grant (to M.B.). This publication uses data from the MalariaGEN Plasmodium vivax Community Project (www.malariagen.net/projects/parasite/pv) and from the Plasmodium vivax Sequencing Project at the Broad Institute of Harvard and MIT (www.broadinstitute.org/) and was supported by Grant U19AI089676 (National Institute of Allergy and Infectious Diseases International Centers of Excellence for Malaria Research). We acknowledge the NIAID-funded Broad Institute Genome Sequencing Center for Infectious Disease and the International Centers for Excellence in Malaria Research for providing genome sequence data prior to publication. We acknowledge the Victorian State Government Operational Infrastructure Support and Australian Government National Health and Medical Research Council Independent Research Institute Infrastructure Support Scheme.enMalariaParasite invasionReticulocyte binding proteinSAXSX-ray crystallography2016-01-1210.1073/pnas.151651211384954565296