Comparison of the Structures and Peptide Binding Specificities of the BRCT Domains of MDC1 and BRCA1
Comparison of the Structures and Peptide Binding Specificities of the BRCT Domains of MDC1 and BRCA1
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DOI：
10.1016/j.str.2009.12.008
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发表时间：
2010-02-10
期刊：
影响因子：
5.7
通讯作者：
Glover, J. N. Mark
中科院分区：
文献类型：
--
作者：
Campbell, Stephen J.;Edwards, Ross A.;Glover, J. N. Mark
BRCA1和MDC1的串联BRCT结构域通过与丝氨酸磷酸化蛋白伴侣的特异性相互作用促进DNA损伤灶的蛋白质信号传导。MDC1 BRCT通过直接识别C端羧酸盐，在组蛋白变体γ H2AX的C端结合pser - gln - glu - tir - coo -，而BRCA1在C端或靶蛋白内部位点识别pSer-X-X-Phe基序。通过荧光偏振结合实验，我们发现虽然这两种brct都倾向于+3位置的游离主链羧酸盐，但这种偏好在MDC1中更为明显。与四肽底物结合的BRCA1和MDC1的晶体结构揭示了保守精氨酸（BRCA1中的Arg1699和MDC1中的Arg1933）环境的差异，这决定了- coo -与- co - nh2末端肽的相对亲和力。MDC1的突变诱导更类似brca1的构象，从而放松了结合特异性，使突变体能够结合缺乏- coo -末端的磷酸肽。
The tandem BRCT domains of BRCA1 and MDC1 facilitate protein signaling at DNA damage foci through specific interactions with serine-phosphorylated protein partners. The MDC1 BRCT binds pSer-Gln-Glu-Tyr-COO- at the C terminus of the histone variant gamma H2AX via direct recognition of the C-terminal carboxylate, while BRCA1 recognizes pSer-X-X-Phe motifs either at C-terminal or internal sites within target proteins. Using fluorescence polarization binding assays, we show that while both BRCTs prefer a free main chain carboxylate at the +3 position, this preference is much more pronounced in MDC1. Crystal structures of BRCA1 and MDC1 bound to tetrapeptide substrates reveal differences in the environment of conserved arginines (Arg1699 in BRCA1 and Arg1933 in MDC1) that determine the relative affinity for peptides with -COO- versus -CO-NH2 termini. A mutation in MDC1 that induces a more BRCA1-like conformation relaxes the binding specificity, allowing the mutant to bind phosphopeptides lacking a -COO- terminus.