Renzoni D A, Pugh D J, Siligardi G, Das P, Morton C J, Rossi C, Waterfield M D, Campbell I D, Ladbury J E
Oxford Centre for Molecular Science, University of Oxford, U.K.
Biochemistry. 1996 Dec 10;35(49):15646-53. doi: 10.1021/bi9620969.
The interaction of the Fyn SH3 domain with the p85 subunit of PI3-kinase is investigated using structural detail and thermodynamic data. The solution structure complex of the SH3 domain with a proline-rich peptide mimic of the binding site on the p85 subunit is described. This indicates that the peptide binds as a poly(L-proline) type II helix. Circular dichroism spectroscopic studies reveal that in the unbound state the peptide exhibits no structure. Thermodynamic data for the binding of this peptide to the SH3 domain suggest that the weak binding (approximately 31 microM) of this interaction is, in part, due to the entropically unfavorable effect of helix formation (delta S0 = -78 J.mol-1.K-1). Binding of the SH3 domain to the intact p85 subunit (minus its own SH3 domain) is tighter, and the entropic and enthalpic contributions are very different from those given by the peptide interaction (delta S0 = +252 J.mol-1.K-1; delta H0 = +44 kJ.mol-1). From these dramatically different thermodynamic measurements we are able to conclude that the interaction of the proline-rich peptide does not effectively mimic the interaction of the intact p85 subunit with the SH3 domain and suggest that other interactions could be important.
利用结构细节和热力学数据研究了Fyn SH3结构域与PI3激酶p85亚基之间的相互作用。描述了SH3结构域与p85亚基上结合位点的富含脯氨酸的肽模拟物的溶液结构复合物。这表明该肽以聚（L-脯氨酸）II型螺旋形式结合。圆二色光谱研究表明，在未结合状态下该肽没有结构。该肽与SH3结构域结合的热力学数据表明，这种相互作用的弱结合（约31 microM）部分是由于螺旋形成的熵不利效应（ΔS0 = -78 J·mol-1·K-1）。SH3结构域与完整的p85亚基（减去其自身的SH3结构域）的结合更紧密，熵和焓的贡献与肽相互作用的贡献非常不同（ΔS0 = +252 J·mol-1·K-1；ΔH0 = +44 kJ·mol-1）。从这些截然不同的热力学测量中我们能够得出结论，富含脯氨酸的肽的相互作用不能有效地模拟完整的p85亚基与SH3结构域的相互作用，并表明其他相互作用可能很重要。
