Cell-free synthesis of the fourth component of guinea pig complement (C4): identification of a precursor of serum C4 (pro-C4).
Polysomes (S-20) from homogenates of guinea pig liver synthesized serum albumin and a precursor of the fourth component of guinea pig complement (C4) in vitro. The C4 precursor (pro-C4) accounted for approximately 0.2% and albumin 4% of the radiolabeled protein precipitable by trichloroacetic acid and not bound to polysomes. Pro-C4 is a single polypeptide chain (molecular weight 200,000) which is then converted to C4, a three-chain (molecular weights 95,000, 78,000 and 31,000) structure linked by interchain disulfide bridges. Pro-C4 was also detected intracellularly in short-term tissue cultures of guinea pig liver. C4 was found in the medium harvested from these cultures.
D000818:Animals; D002474:Cell-Free System; D003181:Complement C4 / Q000096:biosynthesis; D003165:Complement System Proteins / Q000096:biosynthesis; D003513:Cycloheximide / Q000494:pharmacology; D006168:Guinea Pigs; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008970:Molecular Weight; D011498:Protein Precursors / Q000096:biosynthesis
D003181:Complement C4; D011498:Protein Precursors; D003165:Complement System Proteins; D003513:Cycloheximide
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