Insights into binding cooperativity of MATa1/MATa2 from the crystal structure of a MATa1 homeodomain-maltose binding protein chimera
Insights into binding cooperativity of MATa1/MATa2 from the crystal structure of a MATa1 homeodomain-maltose binding protein chimera
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DOI：
10.1110/ps.0219103
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发表时间：
2003-02-01
期刊：
影响因子：
8
通讯作者：
Wolberger, C
中科院分区：
文献类型：
--
作者：
Ke, A;Wolberger, C
酵母MATa1和MATalpha2是同源结构域蛋白，它们与DNA协同结合，抑制细胞类型特异性基因的转录。然而，在缺乏MATa2的情况下，MATa1的DNA亲和力和特异性非常低。MATa1通过与MATalpha2的c端尾相互作用转化为高亲和力的dna结合蛋白。为了理解为什么MATa1自身结合DNA较弱，以及MATalpha2尾部如何影响MATa1对DNA的亲和力，我们确定了麦芽糖结合蛋白(MBP)-a1嵌合体的晶体结构，其DNA结合行为与MATa1相似。在没有alpha2和DNA的情况下确定的MBP-a1结构中的整体MATa1构象与a1/alpha2/DNA结构中的构象相似。唯一的区别在于MATa1的DNA识别螺旋的c端部分，它在目前的结构中是灵活的。然而，这些残基所处的位置不可能受到MATalpha2尾部结合的影响。研究结果反驳了MATalpha2尾部诱导a1构象变化的观点，认为MATalpha2尾部对MATalpha2和MATa1的DNA结合起到了能量偶联作用。
The Yeast MATa1 and MATalpha2 are homeodomain proteins that bind DNA cooperatively to repress transcription of cell type specific genes. The DNA affinity and specificity of MATa1 in the absence of MATa2, however, is very low. MATa1 is converted to a higher affinity DNA-binding protein by its interaction with the C-terminal tail of MATalpha2. To understand why MATa1 binds DNA weakly by itself, and how the MATalpha2 tail affects the affinity of MATa1 for DNA, we determined the crystal structure of a maltosebinding protein (MBP)-a1 chimera whose DNA binding behavior is similar to MATa1. The overall MATa1 conformation in the MBP-a1 structure, which was determined in the absence of alpha2 and DNA, is similar to that in the a1/alpha2/DNA structure. The sole difference is in the C-terminal portion of the DNA recognition helix of MATa1, which is flexible in the present structure. However, these residues are not in a location likely to be affected by binding of the MATalpha2 tail. The results argue against conformational changes in a1 induced by the tail of MATalpha2, suggesting instead that the MATalpha2 tail energetically couples the DNA binding of MATalpha2 and MATa1.