Folding of carboxyl domain and assembly of procollagen I.
Folding of carboxyl domain and assembly of procollagen I.
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发表时间：
1986-07
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通讯作者：
K. Doege;J. Fessler
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作者：
K. Doege;J. Fessler
在放射性标记的鸡胚头骨的乙酸提取物中发现了早期形式的 I 型前胶原。它类似于天然 I 型前胶原，但沉积速度稍快，其组分链羟基化程度稍低，并且彼此之间不存在二硫键连接，尽管其前肽内部是二硫键连接的。脉冲追踪实验表明其转化为二硫键连接的前胶原。由于当脯氨酸羟基化被 2,2'-联吡啶阻断时发生相同的转化，我们推断从其组分链形成该前体不需要胶原三螺旋形成。我们认为，各个前-α (I) 链的折叠羧基前肽之间的相互作用是形成该前体和前胶原 I 的重要步骤。对完全还原和变性的羧基前肽的重折叠和缔合的研究支持了这一概念。根据一些胰蛋白酶肽的图谱判断，在谷胱甘肽存在的情况下，可以重新建立正确的二硫键。个别羧基前肽首先重新折叠，甚至在 2 M 尿素中也会发生这种情况。仅当存在少于 0.5 M 尿素时，才会发生折叠羧基前肽之间的识别。羧基端肽的存在对于三聚体重组很重要。各个前肽也在 pro-α (I) 链的无细胞翻译过程中自发折叠，并被特定抗体识别。我们考虑了羧基前肽在 I 型前胶原分子形成中的作用，并提出了一种自组装模型，该模型可能是通过与粗面内质网管腔表面的相互作用来促进的。
An early form of procollagen I was found in acetic acid extracts of radioactively labeled chick embryo skull bones. It resembled native procollagen I, but sedimented slightly faster, and its component chains were slightly underhydroxylated and were not disulfide-linked to each other, although its propeptides were internally disulfide-bonded. Pulse-chase experiments showed its conversion to disulfide-linked procollagen. As the same conversion occurred when proline hydroxylation was blocked by 2,2'-dipyridyl, we infer that the formation of this precursor from its component chains does not require collagen triple helix formation. We suggest that interaction between the folded carboxyl propeptides of individual pro-alpha (I) chains is an important step in the formation of this precursor and of procollagen I. Studies of the refolding and association of fully reduced and denatured carboxyl propeptides supported this concept. In the presence of glutathione the correct disulfide bonds could be reestablished, as judged by a mapping of some tryptic peptides. Individual carboxyl propeptides refolded first, and this occurred even in 2 M urea. Recognition between folded carboxyl propeptides occurred only when less than 0.5 M urea was present. The presence of the carboxyl telopeptides was important for trimeric reassembly. Individual propeptides also folded spontaneously during cell-free translation of pro-alpha (I) chains and were recognized by specific antibodies. We consider the role of carboxyl propeptides in the formation of procollagen I molecules and suggest a model of self-assembly, possibly facilitated by interactions with the luminal surface of the rough endoplasmic reticulum.