CHARACTERIZATION OF A RIBONUCLEIC-ACID TRANSCRIPT FROM THE BROOK TROUT (SALVELINUS-FONTINALIS) OVARY WITH STRUCTURAL SIMILARITIES TO MAMMALIAN ADIPSIN COMPLEMENT FACTOR-D AND TISSUE KALLIKREIN, AND THE EFFECTSOF KALLIKREIN-LIKE SERINE PROTEASES ON FOLLICLE CONTRACTION

A 2.4-kilobase (kb) clone (kallikrein trout #14; KT-14) was isolated f rom a brook trout ovulatory cDNA library. KT-14 contains an open readi ng frame (ORF) of 768 base pairs (bp), presumably encoding a protein o f 255 amino acids. The KT-14 cDNA also contains a 711-bp 5' untranslat ed region and a 793-bp region downstream of the ORF that includes a 66 -bp sequence repeated 12 times. The amino acid sequence of the KT-14 O RF is 41% identical to that of porcine complement factor D and 33% ide ntical to that of porcine pancreatic kallikrein. On Northern blots of ovarian tissue, KT-14 hybridized with four transcripts of 1.8, 2.4, 2. 9, and 3.2 kb. While the 3.2- and 2.4-kb transcripts were present in t he ovary prior to meiotic maturation, they were significantly up-regul ated at ovulation and at 12 h postovulation, respectively. Antibodies constructed against the recombinant KT-14 protein recognized one 30-kD a immunogenic protein in ovarian tissue and fluid. This immunogenic pr otein was significantly elevated in the tissue by ovulation. Using a f ollicle weight loss bioassay, we provide indirect evidence that mammal ian kallikrein and related serine proteases can stimulate brook trout follicle contraction. Thus, one possible function of the KT-14 protein may be the regulation of oocyte expulsion at ovulation.