Sequence analysis of cDNAs encoding precursors of starfish asterosaps

To understand how starfish sperm activating peptides (asterosaps) are synth esized in the ovary, we cloned cDNAs encoding asterosaps and elucidated the ir nucleotide sequences. The mRNA encoding asterosaps was synthesized only in the oocytes, but not in the follicle cells, and the length was 3.7 kb. T he cDNA clones contained multiple isoforms of asterosaps. We assume that as terosap precursors are large prepolypeptide chains with an unusual "rosary- type" structure made of 10 successive similar stretches of 51-55 residues. Each stretch Finishes with a "spacer" of 17-21 residues immediately followe d by the sequence of one asterosap isoform. The N-terminal of this precurso r has 19-21 successive glutamine-rich repeating units. Maturation of the pr ecursor may require endopeptidases that cleave both C- and N-sites of lysin e-arginine. Dev. Genet. 25. 130-136, 1999. (C) 1999 Wiley-Liss, Inc.