FIBROBLAST GROWTH FACTOR

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 人酸性成纤维细胞生长因子是β-三叶超家族的一员，其三级结构具有三重对称性。然而，这种对称性的证据在初级序列水平上并不是很明显。这表明，虽然可能存在保留(或收敛于)对称三级结构的选择压力，但其他选择压力已导致进化过程中一级序列的分歧。通过对该蛋白家族19个成员的链内和同源序列比较，我们设计了fgf-1的突变体，它限制了核心堆积残基的子集在初级序列水平上具有三重对称性。使用X射线结晶学和差示扫描量热法相结合的方法评估了这些突变对结构和稳定性的影响。突变对结构和稳定性的影响可以通过使用1.0A探头半径探测到的核心内的“微腔”的特征来合理化。结果表明，初级序列内的对称约束与紧密堆积的核心相容，且接近野生型稳定性。然而，尽管总体上保持了总体的热稳定性，但随着初级序列对称性的增加，非两态变性显著增加。因此，折叠的性质，而不是稳定性，可能有助于对称蛋白质结构中不对称初级核心序列的选择压力。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. AbstractHuman acidic fibroblast growth factor (FGF-1) is a member of the beta-trefoil hyperfamily and exhibits a characteristic threefold symmetry of the tertiary structure. However, evidence of this symmetry is not readily apparent at the level of the primary sequence. This suggests that while selective pressures may exist to retain (or converge upon) a symmetric tertiary structure, other selective pressures have resulted in divergence of the primary sequence during evolution. Using intra-chain and homologue sequence comparisons for 19 members of this family of proteins, we have designed mutants of FGF-1 that constrain a subset of core-packing residues to threefold symmetry at the level of the primary sequence. The consequences of these mutations regarding structure and stability were evaluated using a combination of X-ray crystallography and differential scanning calorimetry. The mutational effects on structure and stability can be rationalized through the characterization of 'microcavities' within the core detected using a 1.0A probe radius. The results show that the symmetric constraint within the primary sequence is compatible with a well-packed core and near wild-type stability. However, despite the general maintenance of overall thermal stability, a noticeable increase in non-two-state denaturation follows the increase in primary sequence symmetry. Therefore, properties of folding, rather than stability, may contribute to the selective pressure for asymmetric primary core sequences within symmetric protein architectures.