A protein from the salivary glands of the giant Amazon leech with high sequence homology to a nicotinic acetylcholine receptor subunit

A gene coding for a soluble protein with homology to the beta subunit of th e nicotinic acetylcholine receptor from goldfish was isolated from a cDNA l ibrary of Haementeria ghilianii salivary glands. Comparison of the leech pr otein sequence with the database showed that the N terminus has high homolo gy with the extracellular portion of acetylcholine receptor beta subunits, whilst the C terminus, highly charged, has homology to proteins which may b e involved in chelating divalent cations. The leech protein was expressed i n mammalian cells acid the product compared to the native protein. Both pro teins are glycosylated and form polymers which are disrupted by heat but no t by reducing agents A role for this protein in salivary gland secretion is suggested.