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.
Carr
C
C
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110.
McCourt
D
D
Cohen
J B
JB
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