The egg plasma membrane and cortical structures are highly enriched in protein tyrosine kinase activity which is thought to play an important role in the fertilization process. In order to identify the tyrosine protein kinases in the egg cortex, a site directed polyclonal antibody was produced against a peptide duplicating a conserved region of the catalytic domain of the sea urchin c-abl gene product. The region chosen as an antigen had a high degree of homology (57%) to other protein tyrosine kinases. The antibody was found to bind with a high degree of specificity to a 57 kDa protein tyrosine kinase in S. purpuratus eggs. The antibody was capable of immunoprecipitating the enzyme as a 57 kDa phosphoprotein from purified egg cortex fractions solubilized in NP-40. lmmunoprecipitation was completely inhibited by prior incubation of the antibody with the synthetic peptide used as an antigen. Binding of the antibody completely inhibited kinase activity. However, the immunoprecipitated kinase activity could be eluted from the Sepharosecoupled antibody and was shown to have catalytic activity towards a tyrosine containing peptide substrate. The enzyme also underwent autophosphorylation on tyrosine in vltro. Ultrastructural localization of the kinase by immuno-electron microscopy revealed that the enzyme was primarily restricted to the egg plasma membrane.

The turkey metallothionein gene (tkMT) was isolated from a phage lambda-turkey genomic DNA library by virtue of high identity with chicken MT cDNA. The nucleotide sequences of the proximal 240 bp of the 5'-flanking region, of each of the three exons, and of the intron/exon boundaries were determined. Comparisons of the nucleotide sequences of the tkMT and cMT genes revealed (1) absolute conservation of intronic DNA immediately flanking each respective intron/exon boundary, (2) high conservation (95.6%) of exonic DNA encoding translated regions of the mRNA, and (3) high conservation (95%) of exonic DNA encompassing the putative transcription start point and polyadenylation signals. Sequence comparisons of the tkMT and cMT promoters regions near the TATA box revealed that both promoters contain a highly conserved proximal metal-responsive enhancer (MRE-enhancer) motif. The deduced amino acid sequence (63 amino acids) of tkMT was identical with that of cMT. In order to further explore the degree of conservation of the protein coding regions of avian MT genes, partial MT cDNAs from turkey, quail (qMT), and pheasant (pMT) were amplified using the reverse transcriptase-polymerase chain reaction (RT-PCR) and primers corresponding to the amino- and carboxyl-terminal coding regions of cMT mRNA. RT-PCR reaction products were cloned and the DNA sequences of multiple cDNA clones from each species were determined. The results suggest the existence of a single MT mRNA in zinc-treated liver from turkey and pheasant and the existence of a major and possibly a minor MT mRNA in quail.(ABSTRACT TRUNCATED AT 250 WORDS)