Affinity labeling of multiplication stimulating activity receptors in membranes from rat and human tissues.

摘要: Plasma membranes from rat adipocytes and liver human placenta have been labeled by covalent cross-linking to membrane-bound 125I-labeled multiplication stimulating activity (125I-MSA) with three different bishydroxysuccinimide esters: disuccinimidyl suberate, succinate, ethyleneglycolyl bis(succinimidyl succinate). Dodecyl sulfate-polyacrylamide gel electrophoresis autoradiographic analysis of the 125I-MSA-labeled material in presence dithiothreitol reveals one single-labeled protein migrating an apparent Mr = 255,000 regardless kind concentration cross-linker used. Electrophoresis absence reductant indicates that affinity-labeled species is not disulfide-linked any other native plasma membrane, but contains internal disulfide bonds compact its structure. The labeling increases increasing concentrations 125I-MSA between 0.3 3 nM. Labeling abolished a competitive manner nonradioactive MSA similar insulin, proinsulin, or epidermal growth factor all tissues examined. unique this 225,000 membrane component selective inhibition suggest receptor for MSA.