Conserved proteins as immunogens: glutathione S-transferase of Schistosoma.
Although some immunogenic proteins of parasites evolve rapidly and seem to have no function other than the eliciting o f an immune response, others are proteins that are ordinarily conserved because of functional constraints. The 26 kDa and 28 kDa glutathione S-transferases (GSTs) of Schistosoma would seem to fall in the latter category. However, in the generally more conserved N-terminal portion o f the molecule, the 28 kDa GSTs have evolved over twice as fast at nor-synonymous nucleotide sites as have the 26 kDa GSTs. It is possible that this accelerated rate o f evolution results from natural selection by the host immune system, as discussed here by Austin Hughes.
Department of Biology and the Institute of Molecular Evolutionary Genetics, The Pennsylvania State University, University Park, PA 16802, USA.
A L
AL
Hughes