ALPHA-CRYSTALLIN PROTEIN COGNATES IN EGGS OF THE MOTH, PLODIA-INTERPUNCTELLA - POSSIBLE CHAPERONES FOR THE FOLLICULAR EPITHELIUM YOLK PROTEIN

alpha-Crystallin protein cognates were found in germ cells of the Indi anmeal moth, Plodia interpunctella (Shirk and Zimowska, 1997). A cDNA clone of 674 bp with a single open reading frame was isolated for a 25 000 molecular weight polypeptide member of this family, alpha CP25, an d a single transcript of approximately 700 bp was found in the ovary o f vitellogenic females. Both the DNA sequence and predicted amino acid sequence showed considerable homology with the embryonic lethal gene, l(2)efl, in Drosophila,melanagaster. In addition to the sequence for l(2)efl, the predicted amino acid sequence for alpha cp25 also showed significant sequence similarity with the alpha-crystallin A chain poly peptides from the lenses of vertebrate eyes. An N-terminal hydrophobic aggregation site and a C-terminal protective binding site common to a lpha-crystallin proteins were present in the predicted alpha cp25 and l(2)efl amino acid sequences, while only the C-terminal protective bin ding site was present in the small heat shock protein sequences from D . melanogaster. On the other hand, the cDNA sequence for alpha cp25 sh owed more similarity to small heat shock proteins in D. melanogaster. This evidence suggests that although the alpha-crystallin protein cogn ates in P. interpunctella evolved from a gene common with small heat s hock protein genes, the amino acid sequence has converged on a structu re similar to that of alpha-crystallin proteins. Native immunoblot ana lysis showed that the alpha-crystallin proteins formed high molecular weight complexes with the follicular epithelium yolk protein (FEYP) bu t not vitellin in yolk. An electroblot binding assay was used to show that the germcell alpha-crystallins of P. interpunctella bind specific ally with the FEYP and that the binding was reversible in the presence of ATP or low pH. This evidence in conjunction with the evidence that the alpha-crystallins and FEYP form a stable complex that co-purifies from native egg proteins suggests that the alpha-crystallin cognates function as chaperones for the follicular epithelium yolk proteins in the embryos of P. interpunctella. (C) Published by Elsevier Science Lt d. All rights reserved.