含磷酸结合口袋的BRCT结构域功能位点预测

BRCT( BRCA1 C-terminus)是真核生物DNA损伤修复系统重要的信号传导和蛋白靶向结构域.为了探讨含磷酸结合口袋的BRCT与磷酸化配体结合的机制,对XRCC1 BRCT1、PTIP BRCT4、ECT2 BRCT1和TopBP1BRCT1进行了结构保守性和表面静电势分析.结果显示,4个BRCT的磷酸结合口袋周围所存在的结构保守并带正电势的沟槽很可能是其功能位点,并且类似的沟槽在含磷酸结合口袋的BRCT中普遍存在.沟槽两侧及底部均带有极性氨基酸残基,两侧带正电荷,而底部疏水.这说明沟槽与配体的结合以静电和疏水相互作用为主.沟槽主要位于单个BRCT中,而且4个BRCT的沟槽在形状和电荷分布上都不同,说确明BRCT配体特异性主要由单个BRCT决定.磷酸结合口袋位于沟槽中心,说明沟槽可能同时结合磷酸化残基的N端和C端附近残基.

Functional site prediction of BRCT domain containing phosphate binding pocket

The BRCT domain (after the C-terminal domain of a breast cancer susceptibility protein) is an important signaling and protein targeting motif in the DNA damage response system. To clarify possible interaction mechanisms between the BRCT domain, which contains phosphate binding pocket and its phosphorylated ligand, we analyzed the structural conservation and electrostatic surface potentials of XRCC1 BRCT1, PTIP BRCT4, ECT2 BRCT1 and TopBP1 BRCT1. The results showed common structurally conserved and positively charged grooves located around the phosphate binding pockets of these domains. These grooves possibly act as functional sites in the four BRCT domains due to the extensive existence of similar grooves in the BRCT domains containing phosphate binding pocket. The two sides of the groove were composed of positively charged and hydrophilic residues and the bottom was composed of hydrophobic and hydrophilic residues, suggesting that the groove binds to BRCT domain ligand mainly through electrostatic and hydrophobic interactions. The groove was mainly located in individual BRCT domains and differences in shape and charge distribution among the four BRCT domain grooves were observed, indicating that ligand binding specificity was predominantly determined by individual BRCT domains. The groove was centered by the phosphate binding pocket, implying that the groove interacted with residues located at both the N-terminal and C-terminal sides of the phosphorylated residue.