Characterization of the gene encoding the hemocyanin subunit e from the tarantula Eurypelma californicum.

The gene for the hemocyanin subunit e of the tarantula Eurypelma californicum has been isolated from a genomic phage library by using a corresponding cDNA clone as a probe. The transcriptional unit spans a chromosomal region of about 55 kilobase pairs (kbp). The gene consists of nine exons that are separated by large introns. The intron/exon boundaries were determined by direct comparison of genomic and cDNA sequences. A putative promoter region ("TATA" box, reversed "CAAT" box) 100 bp 5' to the translational initiation codon strongly suggests the presence of a functional gene. The 3' flanking region carries the polyadenylylation signal (AATAAA) and several conserved structures for the 3' splicing of the pre-mRNA. A comparison of the gene architecture of the subunit e gene with the three-dimensional structure of the arthropod hemocyanin subunit shows a good correspondence with the division of the subunit into three domains (two exons coding for the first, three coding for the second, and four coding for the third domain). The relationship to molluscan hemocyanins, different tyrosinases, and the larval serum proteins is discussed.