A novel small protein associated with a conjugated trienoic chromophore from membranes of scallop adductor muscle: phosphorylation by protein kinase A

Abstract

Membranes enriched in sarcolemma from the cross-striated adductor muscle of the deep sea scallop have been found to contain a previously undescribed small protein of 6–8 kDa that can be released by treatment with organic solvent mixtures. This proteolipid co-purified with a non-amino acid chromophore containing a conjugated trienoic moiety. Although common in plants and algae, such a stable conjugated trienoic group is unusual for an animal cell. The N-terminal amino acid sequence of the protein was XEFQHGLFGXF/ADNIGLQ, which most strongly resembles sequences in the triacyl glycerol lipase precursor and the product of the human breast cancer susceptibility gene BRCA 1, but does not show similarity to previously described proteolipids. The protein was found to be one of the major substrates in its parent membrane for the catalytic subunit of protein kinase A, which may imply a regulatory function for this molecule.