MUKAI, S.T.*; HOQUE, M.T.; MORISHITA, F.; SALEUDDIN, A.S.M.; York Univ., Toronto; York Univ., Toronto; Hiroshima Univ., Japan; York Univ., Toronto: Characterization of an important glycoprotein in female reproduction from the freshwater snail (Helisoma duryi)

The albumen gland of pulmonate molluscs is a female accessory sex gland that synthesizes and secretes a complex mixture of polysaccharides and proteins known as perivitelline fluid. The perivitelline fluid is secreted around individual eggs and provides the primary source of nutrition to the developing embryos. A 66 KDa protein was identified from the albumen gland of the freshwater snail Helisoma duryi,which is controlled by a putative brain peptide and the catecholamine dopamine. The protein is an N-linked glycoprotein composed of four 66 KDa subunits, which was separated by SDS-PAGE, and then extracted and subjected to enzymatic digestion. Amino acid sequences from several peptide fragments were analyzed by mass spectroscopy; and degenerate oligonucleotides were designed based upon the amino acid sequences. Using RT-PCR and 5′ and 3′ RACE, the sequence for the entire coding region of the 66 KDa glycoprotein was obtained. The nucleotide sequence predicted a protein with 477 amino acids and having a molecular mass of about 54 KDa. The amino acid sequence shares 75% identity to a partial sequence from a cDNA clone from the albumen gland of B. glabrata. The mRNA for the albumen gland glycoprotein is highly expressed in the albumen gland and to a lesser extent in a few other tissues. The albumen gland glycoprotein is also the major protein present in freshly oviposited egg masses and its amount steadily decreased during embryonic development. The function(s) of the albumen gland glycoprotein and its regulation by potential regulatory factors will be presented.