Structural Studies of Triple-Helical Proteins

一种全面了解氨基酸序列作用的多肽方法 (Gly-X-Y)n对正常和突变胶原三螺旋的稳定性、构象、折叠、动力学和自结合的影响正在进行中。我们的目标是在分子水平上完成序列稳定性的关联；开发多肽来模拟三螺旋自结合；以及追求胶原疾病中发现的甘氨酸替代造成的破坏。之前的主客体多肽研究确定了所有20个氨基酸在X和Y位置的三螺旋倾向，并将完成对三螺旋内分子相互作用的评估。这些Gly-X-Y序列和稳定性之间的关系将被用来预测胶原模型多肽的整体稳定性，并将胶原蛋白的局部稳定性变化与配体结合位置、与纤维形成有关的微展开以及突变的临床严重性联系起来。量热的研究被用来阐明三螺旋的羟脯氨酸稳定的机制，并建议进一步研究最近建立的与序列相关的三螺旋扭曲的调节。一个重要的目标是建立一个多肽系统来模拟三螺旋的自结合，因为胶原蛋白在超分子组装中发挥作用，而且一些胶原突变是病理性的，因为它们影响到高阶结构。设计自结合多肽的策略将包括成对的相反电荷残基以 促进套准阵列和调整粘性末端和重复图案设计以形成 交错阵列。建议对导致骨骼疾病(成骨不全)的I型胶原突变和导致水疱性皮肤病(大疱性表皮松解症)的VII型胶原突变的多肽模型进行研究。将检查突变的直接序列环境的影响以及取代Gly的残基的同一性。通过多肽研究将胶原蛋白的结构、动力学和折叠放在一个固体的物理化学框架中，将为理解自结合和结合的正常生物学活性以及受这种丰富的蛋白质影响的许多疾病中发生的变化提供背景。

A peptide approach to a comprehensive understanding of the effect of amino acid sequence (Gly-X-Y)n on the stability, conformation, folding, dynamics and self-association of the normal and mutant collagen triple-helix is in progress. Our goals are to complete sequence-stability correlations at the molecular level; to develop peptides to model triple-helix self-association; and to pursue the disruption caused by Gly substitutions found in collagen diseases. Previous host-guest peptide studies established the triple-helix propensities of all 20 amino acids for the X and Y positions, and evaluation of molecular interactions within the triple-helix will be completed. These relationships between Gly-X-Y sequence and stability will be used to formulate predictions for the global stability of collagen model peptides and to relate local stability variations along collagen with ligand binding sites, microunfolding implicated in fibril formation, and the clinical severity of mutations. Calorimetric investigations are proposed to elaborate the mechanism of hydroxyproline stabilization of the triple-helix, and studies are proposed to further investigate the recently established sequence related modulation of triple-helix twist. An important goal is to establish a peptide system to model the self-association of triple-helices, since collagens function in supramolecular assemblies and some collagen mutations are pathological because of their influence on higher order structure. Strategies to design self-associating peptides will include pairs of oppositely charged residues to promote in register arrays and adaptation of sticky end and repeating pattern designs to form staggered arrays. Studies are proposed on peptide models of type I collagen mutations leading to a bone disease (osteogenesis imperfecta) and of type VII collagen mutations leading to a blistering skin disease (dystrophoic form of epidermolysis bullosa). The effect of the immediate sequence environment of the mutation and the identity of the residue replacing the Gly will be examined. Placing collagen structure, dynamics, and folding in a solid physicochemical framework through peptide studies will provide a context for understanding normal biological activities of selfassociation and binding, and for the changes occurring in many diseases affected by this abundant protein.