Evolution of the thioester-containing proteins (TEPs) of the arthropoda, revealed by molecular cloning of TEP genes from a spider, Hasarius adansoni.

The thioester-containing protein (TEP) family of genes, found in most Eumetazoan genomes, is classified into two subfamilies: the alpha-2-macroglobulin (A2M) subfamily and the C3 subfamily. Many A2M subfamily members, including insect TEP (iTEP), have been reported from the Arthropoda, whereas the C3 subfamily members have been reported only from two horseshoe crab species thus far. To elucidate the evolution of these genes among the Arthropoda, TEP genes were isolated from a spider, Hasarius adansoni (Chelicerata), by reverse transcription polymerase chain reaction (RT-PCR) amplification using universal degenerate primers specific for the thioester region. Four different TEP genes were identified. Phylogenetic analysis using the entire amino acid sequences of these and various other TEP sequences from the Eumetazoa indicated that two of the spider genes are type C3 (HaadC3-1 and HaadC3-2), one is type A2M (HaadA2M) and the other is closely related to iTEP (HaadiTEP). These results suggest that the common ancestor of the Arthropoda possessed at least three TEP genes, C3, A2M and iTEP and that they were lost differentially in the Crustacean and Hexapodan lineages. Copyright Â