Abstract
The assembly of reduced pro-alpha chains of type I and type II procollagen into the native triple-helical molecule was examined in vitro in the presence and absence of pure protein disulfide isomerase. The data clearly indicates that protein disulfide isomerase is able to accelerate the formation of native interchain disulfide bonds in these procollagens. It takes about 6 min after disulfide bonding before triple-helical molecules exist, while the time required to produce triple-helical type I procollagen in the presence of protein disulfide isomerase is 9.4 min and that for type II procollagen 17.2 min. These values agree with those obtained for type I and II procollagen in vivo suggesting that protein disulfide isomerase is also an enzyme catalyzing interchain disulfide bond formation in procollagen in vivo. The formation of native disulfide bonds can proceed without any enzyme catalysis but then requires the presence of reduced and oxidized glutathione. Bonding is rather slow in such a case, however, resulting in a delay in the formation of the triple helix.
Highlights
The assembly of reduced pro-a chains of type I and disulfide bonds in type I11 procollagen during biosynthesis type I1 procollagen into the native triple-helical mole- [6]
The present paper examines the assembly of reduced pro-a chainsof types I and 11 procollagen into the native triple-helical molecule in the presence and absence of protein disulfide isomerase, with the principal aim of studying whether the latter is an enzyme catalyzing disulfide bond formation in procollagens i n viuo
An increase in the concentrationof the glutathione-oxidizing system tomillimolar level admittedly reduced the time requiredfor formation of the pro-y chain in the case of type I procollagen, but even in this case interchain disulfide bonding and triple helix formation was considerably slower than that found in the presence of protein disulfide isomerase
Summary
If purified collagens or procollagens are denatured i n uitro, the presence of covalent cross-links such as disulfide bonds between the polypeptide chains is required for efficient refolding into a triple-helical conformation [10,11,12,13]. The present paper examines the assembly of reduced pro-a chainsof types I and 11 procollagen into the native triple-helical molecule in the presence and absence of protein disulfide isomerase, with the principal aim of studying whether the latter is an enzyme catalyzing disulfide bond formation in procollagens i n viuo. A study is made of the relationship between interchain disulfide bonding of pro-a chains and triple helix formation in the biosynthesis of procollagen.
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