Biosynthesis and postsynthetic processing of human C3b/C4b inactivator (factor I) in three hepatoma cell lines.
1984; Elsevier BV; Volume: 259; Issue: 10 Linguagem: Inglês
10.1016/s0021-9258(20)82168-1
ISSN1083-351X
AutoresGabriel Goldberger, M. Amin Arnaout, David P. Aden, Robert R. Kay, M Rits, Harvey R. Colten,
Tópico(s)Peptidase Inhibition and Analysis
Resumo15factor I is a two-chain plasma glycoprotein composed of disulfide-linked 50,000-and-38,OOO-dalton subunits.Analysis of its biosynthesis and postsynthetic processing demonstrated that factor I is synthesized as a single chain precursor (pro-I) that undergoes glycosylation and limited proteolysis to generate the native protein.One of three human hepatoma cell lines, HepGZ, secreted factor I predominantly (70-90%) in a single chain pro-I form.The other cell lines secrete factor I predominantly in its two chain native form.The defect in conversion of pro-I to I in HepGZ was protein specific since other multichain proteins, derived from single chain precursors, the third, fourth, and fifth components of complement were processed normally.Further analysis of the inefficient pro-I to I conversion by HepGZ revealed that Xenopus oocytes injected with HepGZ mRNA secreted factor I in a predominantly two-chain form.In addition, the apparent sizes of native factor I, transferrin, and a-l-antitrypsin secreted by the three hepatoma lines differed due to differences in postsynthetic processing.
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