A β‐subclass phosphatidylinositol‐specific phospholipase C from squid (Loligo forbesi) photoreceptors exhibiting a truncated C‐terminus

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Abstract
A PCR-based strategy has been used to isolate a full length cDNA encoding a phosphatidylinositol-specific phospholipase C from a sized cDNA squid ( Loligo forbesi ) retinal library. The predicted protein sequence contains 875 amino acids, with calculated M r 98,181, and has marked similarity with PLC β-isoforms, including conservation of the ‘X’ and ‘Y’ regions. It is unique in having a major C-terminal truncation. A major protein of apparent M r 120,000 estimated by SDS-PAGE has been isolated from squid photoreceptors and identified by partial protein sequence analysis to correspond to the protein sequence predicted from the cDNA clone. This protein has been shown to hydrolyse phosphatidylinositol 4,5-bisphosphate. It is not yet clear whether this represents the major light-activated PLC in squid vision.