FOLDING OF GROUP II INTRON RIBOZYME

在蛋白质中，同步辐射分解的程度取决于 反应性残基的溶剂可及性。 因为溶剂 离散残基的可及性将在以下相互作用后改变： HA蛋白与配体，同步辐射裂解提供了一种方法， 探测这些变化，并结合质谱 分析，鉴定参与配体结合的氨基酸残基。 羟基自由基诱导的蛋白质修饰中HA的变化 相对于蛋白质-配体复合物， 足迹 在结合位点相互作用的Hfor残基。 我们选择 研究人血小板前纤维蛋白（HPP）与 Hpoly-L-脯氨酸作为模型蛋白质-配体复合物，作为其晶体 结构已经阐明了HPP中的特定氨基酸残基， 结合聚-L-脯氨酸，HPP的结构不改变 基本上通过该配体的结合。 聚-L-脯氨酸 如解离所示，肽与HPP强烈相互作用 复杂的常数。 N-末端中的残基Trp 3和Tyr 6 HPP的Lys-C肽与Trp 31一样参与结合。 的 毫秒级X射线照射后残留的未修饰蛋白质部分 通过质谱法测定暴露量， 霍夫时间连同含有Lys-C肽的数据， 蛋白水解后的结合残基。 这些数据与 从蛋白质-配体复合物的辐解来检查 蛋白质的H时间分辨修饰， Hligand.

In proteins, the extent of synchrotron radiolysis is dependent on the solvent accessibility of the reactive residues. Since the solvent accessibility of discrete residues will be altered upon interaction of Ha protein with ligand, synchrotron radiolysis provides a method to probe these changes and, in combination with mass spectrometric analysis, identify the amino acid residues involved in ligand binding. HA change in the hydroxyl radical induced modification of the protein Hversus the protein-ligand complex is representative of a footprint Hfor residues that interact at the binding site. We have chosen to Hstudy the interaction between human platelet profilin (HPP) and Hpoly-L-proline as a model protein-ligand complex, as its crystal structure has elucidated the specific amino acid residues in HPP that bind poly-L-proline and that the structure of HPP is not altered substantially by the binding of this ligand. The poly-L-proline peptide interacts strongly with HPP as indicated by the dissociation constants for the complex . Residues Trp3 and Tyr6 in the N-terminal Lys-C peptide of HPP participate in binding as does Trp31. The fraction of unmodified protein that remains after millisecond x-ray exposure is determined by mass spectrometry and is shown as a function Hof time together with data for the Lys-C peptides that contain the Hbinding residues after proteolysis. These are compared with data from Hradiolysis of the protein-ligand complex to examine changes to the Htime-resolved modification of protein with the incorporation of Hligand.