Molecular characterizations of three distinct Babesia gibsoni rhoptry-associated protein-1s (RAP-1s)

Parasitology. 2009 Sep;136(10):1147-60. doi: 10.1017/S003118200999045X. Epub 2009 Jul 27.


Three cDNAs encoding rhoptry-associated protein 1 (RAP-1) homologues were found in the Babesia gibsoni EST database. Based on similarities to BgRAP-1a, which was identified previously by serological screening of a cDNA merozoite library, the two new genes were designated BgRAP-1b (33.7%) and BgRAP-1c (57%). Mice antiserum raised against each recombinant protein reacted specifically with B. gibsoni parasites as determined by Western blotting, which showed native molecular sizes of the BgRAP-1a (51 kDa), BgRAP-1b (53 kDa) and BgRAP-1c (47 kDa) consistent with predictable molecular weights. Immunofluoresence using these antibodies revealed localization of all BgRAP-1s within the matrix of merozoites; however, BgRAP-1a appeared to diverge from the other two when it was found secreted into the cytoplasm of infected erythrocytes. Apical localization of all 3 BgRAP-1s during the extracellular stage of the parasite combined with their ability to bind a canine erythrocyte membrane fraction was suggestive of a role for these proteins in erythrocyte attachment. Lastly, the ability of these recombinant proteins to be used as diagnostic reagents was tested by ELISA and the sensitivities of BgRAP-1a and BgRAP-1c were found increased through N-terminal truncation. Taken together, our data suggest divergent roles for the 3 BgRAP-1s in the merozoite stage of B. gibsoni.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Babesia / classification
  • Babesia / genetics
  • Babesia / immunology
  • Babesia / metabolism
  • Babesiosis / diagnosis
  • Babesiosis / parasitology
  • Babesiosis / veterinary*
  • Blotting, Western
  • DNA, Protozoan / analysis
  • Dog Diseases / diagnosis*
  • Dog Diseases / parasitology
  • Dogs
  • Enzyme-Linked Immunosorbent Assay
  • Fluorescent Antibody Technique
  • Mice
  • Microscopy, Confocal
  • Molecular Sequence Data
  • Protozoan Proteins* / genetics
  • Protozoan Proteins* / immunology
  • Protozoan Proteins* / metabolism
  • Sequence Analysis, DNA


  • DNA, Protozoan
  • Protozoan Proteins
  • rhoptry-associated protein-1, Babesia

Associated data

  • GENBANK/AB480715
  • GENBANK/AB480716