Formation of Recombinant Human Procollagen I Heterotrimers in a Baculovirus Expression System

Abstract

The present study describes the production of human procollagen I in a baculovirus expression system. Recombinant baculovirus carrying proα1(I) or proα2(I) cDNA was constructed and infected to Sf9 cells. Full-length proα1(I) or proα2(I) chains were synthesized by the cells infected with either of the recombinant viruses. The proα1(I) chains formed pepsin-resistant homotrimers stabilized by interchain disulfide bonds, a small proportion of which was secreted into the culture medium. The proα2(I) chains were not linked into trimers by disulfide bonds and failed to form stable triple helices, although some chains were suggested to exist as dimers or unstable trimers in which only two chains were linked by disulfide bonds. In spite of their non-helicity, the proα2(I) chains were secreted at a higher rate than the proα1(I) chains. Sf9 cells simultaneously synthesized both proα1(I) and proα2(I) chains when the cells were co-infected with the two recombinant viruses. Pepsin-treatment of the product clearly demonstrated the production of procollagen I heterotrimers composed of two proα1(I) chains andone proα2(I) chain, homotrimers of the proα1(I) chains being negligible. This expression system appears to offer a unique means of studying the mechanism of chain association and secretion during procollagen biosynthesis.