title: Biosynthesis of the internal thioester bond of the third component of complement.
abstract: C3-translational product, which was synthesized with rabbit liver mRNA in a reticulocyte lysate protein-synthesizing system, did not react with [14C]methylamine, indicating the lack of an internal thioester bond. Instead, the C3-translational product reacted with iodo[1-14C]acetamide, as determined by gel electrophoresis in the presence of sodium dodecyl sulfate after immunoprecipitation of the product, indicating the presence of a reactive thiol group. When the C3-translational product was treated with rabbit liver homogenate, the product acquired reactivity with [14C]methylamine and lost the reactivity with iodo[1-14C]acetamide. Thus, the liver homogenate seemed to contain a factor (or factors) required for the formation of an internal thioester bond. The factor was partially purified from the liver homogenate by ammonium sulfate precipitation and ion-exchange chromatography on DEAE-cellulose.
mesh_terms: D000818:Animals; D002474:Cell-Free System; D002848:Chromatography, DEAE-Cellulose; D003176:Complement C3 / Q000096:biosynthesis*; D004591:Electrophoresis, Polyacrylamide Gel; D004951:Esterification; D007120:Immunochemistry; D066298:In Vitro Techniques; D007460:Iodoacetamide / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008744:Methylamines / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits
chemical_list: D003176:Complement C3; D008744:Methylamines; D012333:RNA, Messenger; C027451:methylamine; D007460:Iodoacetamide