Structural determinants of phosphoinositide selectivity in splice variants of Grp1 family PH domains
Structural determinants of phosphoinositide selectivity in splice variants of Grp1 family PH domains
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DOI：
10.1038/sj.emboj.7600388
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发表时间：
2004-09-29
期刊：
影响因子：
11.4
通讯作者：
Lambright, DG
中科院分区：
文献类型：
--
作者：
Cronin, TC;DiNitto, JP;Lambright, DG
同源蛋白Grp 1（磷酸肌醇的一般受体）、ARNO（Arf核苷酸结合位点开放剂）和细胞粘连素-1的普列克底物蛋白同源（PH）结构域以异常高的选择性结合磷脂酰肌醇（PtdIns）3，4，5-三磷酸。值得注意的是，剪接变体的不同之处仅在于在β 1/β 2环中插入了单个甘氨酸残基，它们对PtdIns（3，4，5）P-3和PtdIns（4，5）P-2表现出双重特异性。从已知的磷酸肌醇识别模式来看，这种显著特异性转换的结构基础并不明显。在这里，我们报告晶体结构的Grp 1和ARNO PH结构域的双特异性变体，无论是在unliganded形式或复杂的PtdIns（4，5）P-2和PtdIns（3，4，5）P-3的头部基团。与β 1/β 2环的接触丧失，头基方向没有显著变化，这是双特异性变体观察到的PtdIns（3，4，5）P-3亲和力显著降低的原因。相反，PtdIns（4，5）P-2亲和力的小幅增加而不是减少可以通过一种新的结合模式来解释，其中甘氨酸插入消除了与β 1/β 2环的不利相互作用。这些观察结果支持的磷酸肌醇识别的决定因素的系统突变分析。
The pleckstrin homology (PH) domains of the homologous proteins Grp1 (general receptor for phosphoinositides), ARNO (Arf nucleotide binding site opener), and Cytohesin-1 bind phosphatidylinositol ( PtdIns) 3,4,5-trisphosphate with unusually high selectivity. Remarkably, splice variants that differ only by the insertion of a single glycine residue in the beta1/beta2 loop exhibit dual specificity for PtdIns(3,4,5) P-3 and PtdIns(4,5) P-2. The structural basis for this dramatic specificity switch is not apparent from the known modes of phosphoinositide recognition. Here, we report crystal structures for dual specificity variants of the Grp1 and ARNO PH domains in either the unliganded form or in complex with the head groups of PtdIns(4,5) P-2 and PtdIns(3,4,5) P-3. Loss of contacts with the beta1/beta2 loop with no significant change in head group orientation accounts for the significant decrease in PtdIns(3,4,5) P-3 affinity observed for the dual specificity variants. Conversely, a small increase rather than decrease in affinity for PtdIns(4,5) P-2 is explained by a novel binding mode, in which the glycine insertion alleviates unfavorable interactions with the beta1/beta2 loop. These observations are supported by a systematic mutational analysis of the determinants of phosphoinositide recognition.