FIBROBLAST GROWTH FACTOR

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 人酸性成纤维细胞生长因子（FGF-1）是β-三叶超家族的成员，具有特征性的三重对称三级结构。然而，这种对称性的证据在一级层序的水平上并不明显。这表明，虽然可能存在选择性的压力，以保持（或收敛）对称的三级结构，其他选择性的压力，导致在演化过程中的主要序列的分歧。使用这个蛋白质家族的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，其在一级序列的水平上将核心包装残基的子集限制为三重对称。 使用X射线晶体学和差示扫描量热法的组合，这些突变的结构和稳定性的后果进行了评价。突变对结构和稳定性的影响可以通过使用1.0A探针半径检测的核心内的“微腔”的表征来合理化。结果表明，在初级序列的对称约束是兼容的一个良好的包装核心和近野生型稳定性。然而，尽管总体热稳定性的一般维持，但非双态变性的显著增加遵循一级序列对称性的增加。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内的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. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Human 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.