Polypeptides differentially expressed in imaginal discs define the peroxiredoxin family of genes in Drosophila

2D gel electrophoresis followed by microsequencing has been used to purify and identify a protein (catalogued in the database as SSP5111) from Drosophila wing imaginal discs of third instar larvae that showed significant differences in their level of expression when compared with other imaginal discs of the same age. The microsequence data showed identity with amino acids encoded by the human proliferation association gene, pag, which is a thiol-specific antioxidant. By virtue of this homology we have cloned and sequenced two cDNAs that appear to define the peroxiredoxin family of Drosophila. One of them, Jafrac1, encodes the SSP5111 protein searched, had 194 amino acids and mapped in the region 11E in the X chromosome. The other, Jafrac2, encodes a protein of 242 amino acids and mapped in the region 62F in the 3 L chromosome. Both new peroxidases contain two conserved cysteines and share homology with other peroxidases that extends over the entire sequence and ranges between 47% and 76%. An antiserum raised against the SSP5111 protein showed significant changes in the amount of protein in different stages of Drosophila development, being a major product in early embryos. In 2D gels the antibody not only recognizes the SSP5111 polypeptide but also a related one (catalogued in the database as SSP6107) that exhibits identical amino-acid sequence over at least 85% of its sequence. The data also suggest that the SSP5111 polypeptide could be a maternal-effect product.