J Vet Sci.  2006 Sep;7(3):263-270. 10.4142/jvs.2006.7.3.263.

Primary structure of mature SAG1 gene of an Indonesian Toxoplasma gondii and comparison with other strains

• Hartati S
• Kusumawati A
• Wuryastuti H
• Widada JS

• KMID: 1089911
• DOI: http://doi.org/10.4142/jvs.2006.7.3.263

Abstract

Toxoplasma gondii is a persistent protozoan parasite capable of infecting almost any warm-blooded vertebrates. SAG1 (p30) is the prototypic member of a superfamily of surface antigens called SRS (SAG1-related sequence). It constitutes the most abundant and predominant antigen. In this paper the primary structure of mature SAG1 gene of an Indonesian T. gondii isolate is described and sequence comparison is made with published sequence data of 7 other strains or isolates. Sequence comparison indicated that SAG1 is highly conserved through evolution and despite parasite spreading world-wide. Sequences may be divided into two major families, independent of the strain/isolate geographic origin. Variations were mainly localized at the C-terminal half or domain 2 and some clustered in restricted areas. Sequence comparison allowed us to define the Indonesian isolate as genuine virulent RH strain. A phylogenetic tree of Toxoplasma strains/isolates was constructed based on SAG1.

Keyword

Indonesian isolate; p30; RH strain; SAG1; sequence comparison; Toxoplasma gondii

MeSH Terms

Amino Acid Sequence
Animals
Antigens, Protozoan/chemistry/*genetics
Base Sequence
Cloning, Molecular
DNA, Protozoan/chemistry/genetics
Goat Diseases/parasitology
Goats
Indonesia
Molecular Sequence Data
Phylogeny
Polymerase Chain Reaction
Protozoan Proteins/chemistry/*genetics
Sequence Alignment
Sequence Analysis, DNA
Toxoplasma/*genetics/*immunology/isolation&purification
Toxoplasmosis/parasitology
Zoonoses/parasitology

Figure

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  Fig. 1 Nucleotide and amino-acid sequence of mature SAG1 of the Indonesian Toxoplasma isolate IS-1. Nucleotide sequence (lower row) is presented as codons and the nucleotide numbering is given. The first t of the first codon ttc is taken as nucleotide number 1. The deduced amino-acid sequence (upper row) is presented with one-letter code, and the corresponding amino-acid hence codon numbering indicated.

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  Fig. 2 Comparison of nucleotide sequence of mature SAG1 gene with SAG1 sequences of 7 other T. gondii strains or isolates. Alignment was carried out using an algorithm developed by Corpet [2]. Sequences are presented as codons. Nucleotide (left, upper) and codon (right, in brackets) numberings are indicated. The stop codon tga (codon no. 260, bases 778-780) is underlined and in italics. Codons with nucleotide variation are underlined and the variations indicated by bold characters. Con, consensus sequence. Sequence accession numbers are as follows: IS-1, AY651825 (Indonesian isolate); CB, X14080 (clone P30.5Cos1); CS, S63900 (strain C); RH1, AY217784 (strain RH); RH2, S76248 (strain RH); PS, S85174 (strain P); ZS, S73634 (Chineese isolate); NT, AF110182 (strain NT).

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  Fig. 3 Phylogenetic tree of T. gondii mature SAG1 (p30) sequences. Sequence alignment and phylogenetic tree were carried out, using an algorithm established by Corpet [2]. RI1 is IS1 in Fig. 1 and 2 and Table 1. The definition of strains or isolates and the respective accession numbers are as in Fig. 2.

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