The 43-kilodalton protein of Torpedo nicotinic postsynaptic membranes: purification and determination of primary structure.
The primary structure of the 43-kilodalton peripheral membrane protein (43-kDa protein) of Torpedo nicotinic postsynaptic membrane has been determined. The 43-kDa protein, which was isolated by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis, has an amino terminus resistant to Edman degradation, while the sequence at the carboxyl terminus is Tyr-Val. An amino acid sequence of 405 residues was obtained by NH2-terminal sequence analysis of complementary peptides generated by digestion with trypsin, chymotrypsin, Staphylococcus aureus V8 protease, and endoproteinase Lys-C, as well as by chemical cleavage at methionine. This sequence of molecular mass 45,618 daltons lacks the amino terminus but extends to the carboxyl terminus of the 43-kDa protein. Unusual structural features of the 43-kDa protein include two regions of approximately 80 residues, each containing 10% cysteine, as well as stretches predicted to exist as amphipathic alpha-helices. Other than the group blocking the amino terminus, no evidence was found for posttranslational modification of amino acids. The 43-kDa protein may represent a novel protein family because a computer search of this sequence with the National Biomedical Research Foundation data base (Release 12.0) did not reveal any significant homology to known protein sequences.
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110.
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D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004557:Electric Organ / Q000378:metabolism*; D007460:Iodoacetamide / Q000378:metabolism; D008565:Membrane Proteins / Q000302:isolation & purification* / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011950:Receptors, Cholinergic / Q000302:isolation & purification*; D011978:Receptors, Nicotinic / Q000302:isolation & purification*; D013569:Synapses / Q000378:metabolism; D014101:Torpedo
D008565:Membrane Proteins; D011950:Receptors, Cholinergic; D011978:Receptors, Nicotinic; D007460:Iodoacetamide