A single mRNA encodes multiple copies of the egg peptide speract

Abstract

A complementary DNA clone (2.3 kb) that encodes the egg peptide speract (Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly) has been isolated from an ovary cDNA library of the sea urchin. Stronglyocentrotus purpuratus. The DNA sequence predicts an open reading frame of 296 amino acids. The likely site of initiation, however, is a downstream in-frame translation initiation codon that would result in a polypeptide of 260 amino acids containing 10 decapeptides, each separated by a single lysine residue. Four of the peptides are speract, and six have the predicted structures of Gly-Phe-Ala-Leu-Gly-Gly-Gly-Gly-Val-Gly (occurs twice), Gly-Phe-Asn-Leu-Asn-Gly-Gly-Gly-Val-Gly, Gly-Phe-Ser-Leu-Thr-Gly-Gly-Gly-Val-Gly, Gly-Thr-Met-Pro-Thr-Gly-Ala-Gly-Val-Asp, and Ile-Asp-His-Asp-Thr-Leu-Ala-Ser-Val-Ser. The isolated cDNA insert hybridized to two species of ovarian mRNA (1.2 and 2.3 kb) obtained from species known to produce speract or speract-like peptides, but failed to hybridize to RNA from other species. Subsequently, a second ovarian cDNA clone (1.2 kb) was isolated and sequenced; this clone contained two additional potential decapeptides: Ser-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly and Ser-Thr-Met-Pro-Thr-Gly-Ala-Gly-Val-Asp. The various speract and speract-like peptides found in egg-conditioned media, therefore, reflect, in part, variable structures within a single copy of mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Sperm-activating peptides in the regulation of ion fluxes, signal transduction and motility

“…SAPs function as moderate, though not complete, species-specific molecules since species that belong to the same taxonomic order share the same class of SAPs (Suzuki, 1995). One sea urchin species can produce different SAP isoforms; one gene encodes multiple SAPs, which are connected in tandem with a spacer amino acid (or several amino acids) forming a large precursor protein (Matsumoto et al, 1999;Ramarao et al, 1990). Interestingly, speract and its isoforms are not synthesized in the oocyte but in the accessory cells that surround the oocyte (Suzuki, 1995), in contrast to the starfish Asterias amurensis where SAPs, called asterosaps, are synthesized by the oocyte itself (Matsumoto et al, 1999).…”

Fertilization in Animals

“…In sea urchins, cDNA clones of SAP precursors have been isolated; it has been found that a single mRNA encodes multiple isoforms of SAPs that are synthesized in follicle cells [Romarao et al, 1990;Kinoh et al, 1994]. To investigate the situation in starfish, Matsumoto et al [1999, this issue) cloned cDNAs encoding SAPs and determined their sequences.…”

Muscarinic agents modify kinetics properties of membrane‐bound guanylyl cyclase activity

“…Thus, positive cooperativity appears to be a characteristic of guanylyl cyclase in its native membrane environment. It was shown recently that highly purified particulate guanylyl cyclase from sea urchin spermatozoa retained positive cooperativity kinetics [38]. Such behaviour could be subsequently converted to that for Michaelis-Menten kinetics by dephosphorylation.…”