Proteolytic fragments of the nicotinic acetylcholine receptor identified by mass spectrometry: implications for receptor topography.

摘要: A triple-state quadrupole or a tandem Fourier-transform mass spectrometer was used to detect and sequence the peptides released by proteolytic cleavage of acetylcholine receptor (AcChR) from Torpedo californica electroplax. Fragments in range up 3479 daltons were characterized on above instrumentation determine proteolytically accessible sites receptor. These data consistent with points determined for membrane-bound fragments same AcChR samples using gas-phase microsequencing. Each subunit is readily cleaved near C-terminus region between proposed transmembrane hydrophobic alpha-helices MIII MIV. This includes putative regulatory phosphorylation amphipathic alpha-helix. Cleavage also observed N-terminal domain, but occurs much more slowly than C-terminal region. No detected middle third receptor, which MI MII. An evaluation these terms topography synaptic extracellular disposition