c端前体结构域的排列引发三螺旋结构，三螺旋结构在c - n方向以拉链的方式传播。这发生在粗面内质网(Engel & Prockop, 1991)。与球状蛋白和卷曲-卷曲结构的折叠相比，胶原蛋白的浓度无关折叠步骤极其缓慢(Bächinger et al. 1980)。三螺旋的形成结合了一个快速的过程(被解释为没有顺式残基的区域折叠)和一个缓慢的过程(被顺式到反式脯氨酸异构化的缓慢动力学限制)(Bächinger et al. 1978)。在没有顺式-脯氨酸键的区域，三螺旋的形成速度是受脯氨酸异构化反应限制的3-4倍(Bachmann et al. 2005)。转换为反式是必需的，因为只有反肽键可以合并到胶原的三重螺旋结构中(Zeng et al. 1998)。高效的螺旋折叠需要3-脯氨酸羟基化复合物的存在。这种Prolyl 3-羟化酶1 (LEPRE1)、Cyclophilin B (CyPB)，也称为肽基- Prolyl顺-反式异构酶B (PPIB)和CRTAP的三聚体具有3-prolyl羟化酶、PPIase和前胶原蛋白伴基的性质(Ishikawa et al. 2009, van Dijk et al. 2009)。有效的折叠需要额外的胶原蛋白特异性伴侣，如Serpin H1 (HSP47 - Smith et al. 1995)。CyPB属于环孢素，是一类保守的胞内和/或分泌蛋白，最初被鉴定为免疫抑制药物环孢素a的细胞结合蛋白。它们是肽基-脯氨酸顺反异构酶(PPIases)，催化肽键的顺反异构化。 CyPB localises to the rough ER but is also secreted extracellularly. It directly interacts with procollagen and is believed to be responsible for converting procollagen cis- to trans-conformers (Zeng et al. 1998). CyPB and Serpin H1 are also involved in procollagen export and secretion. Results obtained with collagen peptides suggest that variations in the Gly-X-Y sequence are likely to result in a non-uniform helical twist along the length of a collagen fibril. Sequences poor in imino acids will have a symmetry close to 10 tripeptide units for every 3 turns of the triple helix (10/3), while stretches of Gly-Pro-Hyp units may have 7/2 symmetry (Brodsky & Persikov 2005).