title: Definition of structural elements in Plasmodium vivax and P. knowlesi Duffy-binding domains necessary for erythrocyte invasion.
abstract: Plasmodium vivax and P. knowlesi use the Duffy antigen as a receptor to invade human erythrocytes. Duffy-binding ligands belong to a family of erythrocyte-binding proteins that bind erythrocyte receptors to mediate invasion. Receptor-binding domains in erythrocyte-binding proteins lie in conserved cysteine-rich regions called Duffy-binding-like domains. In the present study, we report an analysis of the overall three-dimensional architecture of P. vivax and P. knowlesi Duffy-binding domains based on mild proteolysis and supportive-functional assays. Our proteolysis experiments indicate that these domains are built of two distinct subdomains. The N-terminal region from Cys-1-4 (C1-C4) forms a stable non-functional subdomain. The region spanning C5-C12 forms another subdomain, which is capable of binding Duffy antigen. These subdomains are joined by a protease-sensitive linker. Results from deletion constructs, designed for expression of truncated proteins on COS cell surface, show that regions containing C5-C8 of the Duffy-binding domains are sufficient for the binding receptor. Therefore the central region of Duffy-binding domains, which is flanked by two non-functional regions, is responsible for receptor recognition. Moreover, the minimal Duffy-binding region identified here is capable of folding into a functionally competent module. These studies pave the way for understanding the architecture of Duffy-binding domains and their interactions with host receptors.
authors.affiliation: Malaria Research Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Saurabh K
authors.initials: SK
authors.lastname: Singh
authors.forename: Agam P
authors.initials: AP
authors.lastname: Singh
authors.forename: Sunita
authors.initials: S
authors.lastname: Pandey
authors.forename: Syed S
authors.initials: SS
authors.lastname: Yazdani
authors.forename: Chetan E
authors.initials: CE
authors.lastname: Chitnis
authors.forename: Amit
authors.initials: A
authors.lastname: Sharma
mesh_terms: D000818:Animals; D000953:Antigens, Protozoan / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D001665:Binding Sites; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000502:physiology; D003001:Cloning, Molecular; D017931:DNA Primers; D004912:Erythrocytes / Q000469:parasitology*; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010446:Peptide Fragments / Q000737:chemistry; D016790:Plasmodium knowlesi / Q000472:pathogenicity*; D010966:Plasmodium vivax / Q000472:pathogenicity*; D016133:Polymerase Chain Reaction; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion; D014357:Trypsin
chemical_list: D000953:Antigens, Protozoan; D015815:Cell Adhesion Molecules; D017931:DNA Primers; C066001:Duffy antigen binding protein, Plasmodium; D010446:Peptide Fragments; D015800:Protozoan Proteins; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D014357:Trypsin