Synthesis of Albumin via a Precursor Protein in Cell Suspensions from Rat Liver

Open Access
Publisher Website
Google Scholar
Abstract
The mechanism of the biosynthesis of albumin was studied in cell suspensions from rat liver. The cells were prepared by continuous perfusion of the liver in situ with 0.05% collagenase and 0.10% hyaluronidase and incubated under conditions optilnized for the incorporation of amino acids into protein. Seven minutes after starting the incubation l-[1-14C]leucine was added, followed after 25 min by a 15 or 30-min chase with an 830-fold excess of non-radioactive l-leucine. Total protein, an albumin-like protein, and albumin were isolated from samples withdrawn immediately after addition of non-radioactive leucine and after the 15 and 30-min chases. The specific radioactivity of total protein was found to remain constant after addition of the non-radioactive l-leucine, whereas that of the albumin-like protein decreased and that of albumin increased with incubation time. The increase in albumin radioactivity accounted for the decrease in radioactivity of the albuminlike protein, suggesting that the latter is a precursor of albumin. The precursor protein differed from albumin by an oligopeptide extension at the N-terminal end.