FOLDING MECHANISM OF THE TRIPLE HELIX IN TYPE-III COLAGEN AND TYPE-III PN-COLLAGEN - ROLE OF DISULFIDE BRIDGES AND PEPTIDE-BOND ISOMERIZATION
FOLDING MECHANISM OF THE TRIPLE HELIX IN TYPE-III COLAGEN AND TYPE-III PN-COLLAGEN - ROLE OF DISULFIDE BRIDGES AND PEPTIDE-BOND ISOMERIZATION
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DOI：
10.1111/j.1432-1033.1980.tb04610.x
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发表时间：
1980-01-01
期刊：
影响因子：
--
通讯作者：
ENGEL, J
中科院分区：
文献类型：
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作者：
BACHINGER, HP;BRUCKNER, P;ENGEL, J
通过旋光度和圆二色性跟踪III型pN-胶原、III型胶原和III型胶原的四分之一片段中三螺旋形成的动力学。用胰蛋白酶消化和聚丙烯酰胺凝胶电泳检测动力学中间产物。在25°C下重折叠的终产物根据它们的解链曲线、分子量和沉降行为与天然分子相同。仅在低温（4-15°C）下形成稳定性较低的失配结构。在25°C下，螺旋形成仅在三个二硫桥处开始，所述三个二硫桥在羧基末端连接三条链。三重螺旋的生长以拉链状的方式以相当均匀的速率从这个单核中进行。这在转化的大部分上产生零级动力学。因此，半转化的时间与分子的长度成比例。从中间体的出现和消失可以直接观察到三螺旋的生长。螺旋增长的速率取决于肽键顺式→反式异构化的速率。一个模型机制被开发出来，它用一组参数定量描述了整个动力学以及中间体的时间过程：顺式→反式异构化的速率常数k = 0.015 s− 1，在不间断的残基延伸中平均有30个三肽单元，所有的肽键都处于反式构型。
The kinetics of triple‐helix formation in type III pN‐collagen, type III collagen and a quarter fragment of type III collagen was followed by optical rotation and circular dichroism. Kinetic intermediates were detected by trypsin digestion and polyacrylamide gel electrophoresis. The end products of refolding at 25°C were identical to the native molecules according to their melting profiles, molecular weights and sedimentation behavior. Only at low temperatures (4–15°C) were mismatched structures of lower stability formed. At 25°C helix formation started exclusively at the set of three disulfide bridges which link the three chains at the carboxy‐terminal end. The growth of the triple helix proceeds from this single nucleus at a rather uniform rate in a zipper‐like fashion. This gives rise to zero‐order kinetics over a large fraction of the conversion. Consequently the time of half conversion is proportional to the length of the molecule. From the appearance and disappearance of intermediates the growth of the triple helix could be observed directly. The rate of helix propagation is determined by the rate ofcis → transisomerization of peptide bonds. A model mechanism was developed which quantitatively described the overall kinetics as well as the time course of the intermediates with a single set of parameters: the rate constant ofcis → transisomerizationk= 0.015 s−1and an average number of 30 tripeptide units in uninterrupted stretches of residues with all peptide bonds intransconfiguartion.