The acetylcholine receptor of Torpedo californica is an oligomeric glycoprotein which is embedded in the membrane of the multinucleated electroplaque cells of the electric organ. The arrangement of the subunits of the receptor may be an important indication of their function. I propose to study this arrangement by chemical crosslinking in order to map the nearest neighbor proteins of each subunit and by surface labeling, enzymatic proteolysis, and chemical fragmentation in order to determine the exposure of each subunit at the cytoplasmic and external surfaces of the membrane. A primary culture of the electroplaque precursor cells will be isolated for the purpose of studying the biogenesis of the acetylcholine receptor. Both receptor synthesis and degradation will be investigated. The synthesis of the receptor may be regulated at the transcriptional, posttranscriptional or translational levels. The control mechanisms will be studied by isolating mRNA and using this mRNA as a template for in vitro translation.