Breeze A L, Kara B V, Barratt D G, Anderson M, Smith J C, Luke R W, Best J R, Cartlidge S A
Protein Structure Laboratory, Zeneca Pharmaceuticals, Mereside, Alderley Park, Cheshire, UK.
EMBO J. 1996 Jul 15;15(14):3579-89.
We have determined the solution structure of the C-terminal SH2 domain of the p85 alpha subunit of human phosphatidylinositol (PI) 3-kinase (EC 2.7.1.137) in complex with a phosphorylated tyrosine pentapeptide sequence from the platelet-derived growth factor receptor using heteronuclear nuclear magnetic resonance spectroscopy. Overall, the structure is similar to other SH2 domain complexes, but displays different detail interactions within the phosphotyrosine binding site and in the recognition site for the +3 methionine residue of the peptide, the side chain of which inserts into a particularly deep and narrow pocket which is displaced relative to that of other SH2 domains. The contacts made within this +3 pocket provide the structural basis for the strong selection for methionine at this position which characterizes the SH2 domains of PI3-kinase. Comparison with spectral and structural features of the uncomplexed domain shows that the long BG loop becomes less mobile in the presence of the bound peptide. In contrast, extreme resonance broadening encountered for most residues in the beta D', beta E and beta F strands and associated connecting loops of the domain in the absence of peptide persists in the complex, implying conformational averaging in this part of the molecule on a microsecond-to-millisecond time scale.
我们利用异核核磁共振光谱法确定了人磷脂酰肌醇（PI）3激酶（EC 2.7.1.137）p85α亚基C端SH2结构域与来自血小板衍生生长因子受体的磷酸化酪氨酸五肽序列形成的复合物的溶液结构。总体而言，该结构与其他SH2结构域复合物相似，但在磷酸酪氨酸结合位点以及肽段+3位甲硫氨酸残基的识别位点内显示出不同的细节相互作用，该甲硫氨酸残基的侧链插入到一个特别深且窄的口袋中，该口袋相对于其他SH2结构域的口袋发生了位移。在这个+3口袋内形成的接触为该位置强烈选择甲硫氨酸提供了结构基础，这是PI3激酶SH2结构域的特征。与未结合肽段的结构域的光谱和结构特征进行比较表明，在结合肽段的情况下，长BG环的流动性降低。相比之下，在无肽段时该结构域的βD'、βE和βF链以及相关连接环中的大多数残基遇到的极端共振展宽在复合物中仍然存在，这意味着该分子的这一部分在微秒到毫秒的时间尺度上存在构象平均化。
