Makareeva Elena, Mertz Edward L, Kuznetsova Natalia V, Sutter Mary B, DeRidder Angela M, Cabral Wayne A, Barnes Aileen M, McBride Daniel J, Marini Joan C, Leikin Sergey
Section on Physical Biochemistry, Bone and Extracellular Matrix Branch, NICHD, National Institutes of Health, Bethesda, MD 20892, USA.
J Biol Chem. 2008 Feb 22;283(8):4787-98. doi: 10.1074/jbc.M705773200. Epub 2007 Dec 11.
We investigated regions of different helical stability within human type I collagen and discussed their role in intermolecular interactions and osteogenesis imperfecta (OI). By differential scanning calorimetry and circular dichroism, we measured and mapped changes in the collagen melting temperature (DeltaTm) for 41 different Gly substitutions from 47 OI patients. In contrast to peptides, we found no correlations of DeltaTm with the identity of the substituting residue. Instead, we observed regular variations in DeltaTm with the substitution location in different triple helix regions. To relate the DeltaTm map to peptide-based stability predictions, we extracted the activation energy of local helix unfolding (DeltaG) from the reported peptide data. We constructed the DeltaG map and tested it by measuring the H-D exchange rate for glycine NH residues involved in interchain hydrogen bonds. Based on the DeltaTm and DeltaG maps, we delineated regional variations in the collagen triple helix stability. Two large, flexible regions deduced from the DeltaTm map aligned with the regions important for collagen fibril assembly and ligand binding. One of these regions also aligned with a lethal region for Gly substitutions in the alpha1(I) chain.
我们研究了人I型胶原蛋白中不同螺旋稳定性的区域，并讨论了它们在分子间相互作用和成骨不全（OI）中的作用。通过差示扫描量热法和圆二色性，我们测量并绘制了47例OI患者41种不同甘氨酸（Gly）替代物的胶原蛋白解链温度（ΔTm）变化情况。与肽不同，我们发现ΔTm与替代残基的身份没有相关性。相反，我们观察到ΔTm随不同三螺旋区域中替代位置的规律变化。为了将ΔTm图谱与基于肽的稳定性预测相关联，我们从已报道的肽数据中提取了局部螺旋解折叠的活化能（ΔG）。我们构建了ΔG图谱，并通过测量参与链间氢键的甘氨酸NH残基的H-D交换率对其进行了测试。基于ΔTm和ΔG图谱，我们描绘了胶原蛋白三螺旋稳定性的区域变化。从ΔTm图谱推导的两个大的柔性区域与对胶原纤维组装和配体结合重要的区域对齐。其中一个区域也与α1（I）链中甘氨酸替代的致死区域对齐。
