Nucleotide sequence of cloned cDNAs coding for preprosecapin, a major product of queen-bee venom glands

Total mRNA from queen-bee venom glands was transcribed into cDNA and cloned into the PstI and ClaI site of pBR322. The nucleotide sequence of two clones (pUM9/24 and pBMC1) with inserts derived from mRNAs for preprosecapin is presented. The two inserts, which are identical in their overlapping regions, have a coding region encompassing 77 triplets. The cloned cDNAs differ in the length of the 3'-untranslated region, which is about twice as long in clone pUM9/24. The postulated amino acid sequence of preprosecapin starts with a signal peptide containing an estimated 32 residues, followed by a pro part which terminates with a single arginine. The end-product secapin is located at the COOH end of the precursor. Activation of prosecapin must, therefore, differ from the processing of promelittin synthesized in the same gland. Cell-free translation of total venom gland mRNA in the presence of radioactive histidine yields only two major products, the smaller of which is presumably preprosecapin. Edman degradation of total translation products yields peaks of radioactive tyrosine and histidine at the 4th and 10th cycles respectively. This confirms the sequence of preprosecapin deduced from the cDNA clones. The content of secapin in queen-bee venom must be higher than it is in worker bee venom.