title: Sulphydryl groups and iodo-[3H]acetic acid labeling in proteolipids from Torpedo electroplax.
abstract: Several fractions of proteolipids from Torpedo electroplax were separated by DEAE-cellulose chromatography in organic solvents, and the sulphydryl groups were determined by a spectrophotometric method. On the same fractions the covalent labeling with iodo-[3H]acetic acid to sulphydryl groups was studied. In total proteolipids there were 30.3 nmol/mg protein of sulphydryl groups of which 20.6 nmoles were in the form of disulfide bonds and 10.9 nmol as free--SH groups. The highest content of sulphydryl groups (36.7 nmol/mg protein) was found in fraction II; while fraction I, that binds the cholinergic ligands, has a lower content (23.7 nmol/mg protein). The 42 Kdaltons polypeptide, which is the major band in Fraction II, has the strongest labeling with iodo-[3H]acetic acid, while the 39 Kdaltons cholinergic polypeptide shows a lower labeling. The importance of proteolipids as channel-forming macromolecules is discussed in connection with the possible significance of the 42 Kdaltons polypeptide.
mesh_terms: D000818:Animals; D004557:Electric Organ / Q000378:metabolism*; D007461:Iodoacetates / Q000378:metabolism* / Q000494:pharmacology; D019807:Iodoacetic Acid; D007700:Kinetics; D011510:Proteolipids / Q000096:biosynthesis* / Q000302:isolation & purification; D013438:Sulfhydryl Compounds / Q000032:analysis; D014101:Torpedo; D014316:Tritium
chemical_list: D007461:Iodoacetates; D011510:Proteolipids; D013438:Sulfhydryl Compounds; D014316:Tritium; D019807:Iodoacetic Acid