A new locus (vsp417-4) belonging to the tsa417-like subfamily of variant-specific surface protein genes in Giardia intestinalis

Mol Biochem Parasitol. 1999 Mar 15;99(1):55-68. doi: 10.1016/s0166-6851(98)00183-2.


A new variant-specific surface protein gene locus (vsp417-4) of Giardia intestinalis is described. Vsp417-4 represents the fourth member of a gene subfamily that is based on a previously described gene, tsa417 ( =vsp417-1). The new locus was detected by characterising DNA amplified in polymerase chain reactions from the 3' ends of divergent homologues (vsp417-4(A-I), vsp417-4(A-II)) found respectively in isolates belonging to the genetic Assemblage A/Group I ('A-I') and Assemblage A/Group II ('A-II') subtypes of G. intestinalis. The complete vsp417-4(A-I) gene was isolated on a 6.2-kb HindIII fragment by screening a genomic DNA library prepared from a type A-I isolate, Ad-1/C7. The deduced polypeptide (VSP417-4(A-I); 709 amino acids, Mr 72662) has properties characterising it as a Giardia variant-specific surface protein, namely a high cysteine content (11.85 mol%), 29 copies of the four amino-acid 'CXXC' motif, and conserved N-terminal signal peptide and C-terminal hydrophobic (membrane-spanning) segments--the latter terminating with the invariant, hydrophilic motif '-CRGKA'. An extended polyadenylation signal sequence (CTTAGRTAGTAAAY), which appears to be a characteristic feature of VSP genes in Giardia, is situated immediately beyond the stop codon. VSP417-4(A-I) shares 87% sequence identity with VSP417-4(A-II) over its C-terminal 235 amino acids, but only 57-58% identity with VSP417-1, VSP417-2 and VSP417-3 which are encoded by other vsp417 family genes identified in these genotypes. Southern hybridisations, using probes derived from the 5' segment of vsp417-4(A-I), indicated the presence of at least five to six closely related loci in both type A-I and type A-II isolates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Amino Acid Sequence
  • Animals
  • Antigens, Protozoan / chemistry
  • Antigens, Protozoan / genetics*
  • Antigens, Surface / chemistry
  • Antigens, Surface / genetics*
  • Blotting, Southern
  • Evolution, Molecular
  • Genes, Protozoan*
  • Giardia lamblia / classification
  • Giardia lamblia / genetics*
  • Humans
  • Molecular Sequence Data
  • Multigene Family
  • Phylogeny
  • Polymerase Chain Reaction / methods
  • Protozoan Proteins*
  • Restriction Mapping
  • Sequence Alignment
  • Sequence Analysis, DNA


  • Antigens, Protozoan
  • Antigens, Surface
  • Protozoan Proteins
  • variant surface protein H7, Giardia lamblia

Associated data

  • GENBANK/AF065168
  • GENBANK/AF065600
  • GENBANK/AF065601
  • GENBANK/U89152
  • GENBANK/U89153