The C‐terminal extrahelical peptide of type I collagen and its role in fibrillogenesis in vitro: Effects of Ethylurea

Ethylurea was used to weaken hydrophobic interactions during collagen fibrillogenesis in vitro. Intact and enzyme‐digested type I collagen was studied. In all preparations, ethylurea decreased the extent and rate of fibril formation, inhibition being greatest in the enzyme‐digested collagens. With intact collagen (and probably also with carboxypeptidasedigested collagen), there was no evidence the ethylurea altered the mechanism of fibril growth; in pepsin‐digested collagen, however, the growth mechanism was altered by ethylurea, possibly reflecting a conformational change of the “hydrophobic cluster” in the C‐terminal peptide. Such a structural change could occur in a hydrophobic environment once the distal portion of the C‐terminal peptide (presumed to be essential for its structural stability) is removed by pepsin. The results further emphasize the importance of hydrophobic interactions in collagen fibril nucleation and growth in vitro .