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首页> 外文期刊>Journal of Molecular Biology >NMR structure of the hRap1 Myb motif reveals a canonical three-helix bundle lacking the positive surface charge typical of Myb DNA-binding domains
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NMR structure of the hRap1 Myb motif reveals a canonical three-helix bundle lacking the positive surface charge typical of Myb DNA-binding domains

机译：hRap1 Myb基序的NMR结构揭示了规范的三螺旋束，缺乏典型的Myb DNA结合域的正表面电荷

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摘要

Mammalian telomeres are composed of long tandem arrays of double-stranded telomeric TTAGGG repeats associated with the telomeric DNA-binding proteins, TRF1 and TRF2. TRF1 and TRF2 contain a similar C-terminal Myb domain that mediates sequence-specific binding to telomeric DNA. In the budding yeast, telomeric DNA is associated with scRap1p, which has a central DNA-binding domain that contains two structurally related Myb domains connected by a long linker, an N-terminal BRCT domain, and a C-terminal RCT domain. Recently, the human ortholog of scRap1p (hRap1) was identified and shown to contain a BRCT domain and an RCT domain similar to scRap1p. However, hRap1 contained only one recognizable Myb motif in the center of the protein. Furthermore, while scRap1p binds telomeric DNA directly, hRap1 has no DNA-binding ability. Instead, hRap1 is tethered to telomeres by TRF2. Here, we have determined the solution structure of the Myb domain of hRap1 by NMR. It contains three helices maintained by a hydrophobic core. The architecture of the hRap1 Myb domain is very close to that of each of the Myb domains from TRF1, scRap1p and c-Myb. However, the electrostatic potential surface of the hRap1 Myb domain is distinguished from that of the other Myb domains. Each of the minimal DNA-binding domains, containing one Myb domain in TRF1 and two Myb domains in scRap1p and c-Myb, exhibits a positively charged broad surface that contacts closely the negatively charged backbone of DNA. By contrast, the hRap1 Myb domain shows no distinct positive surface, explaining its lack of DNA-binding activity. The hRap1 Myb domain may be a member of a second class of Myb motifs that lacks DNA-binding activity but may interact instead with other proteins. Other possible members of this class are the c-Myb R1 Myb domain and the Myb domains of ADA2 and Adf1. Thus, while the folds of all Myb domains resemble each other closely, the function of each Myb domain depends on the amino acid residues that are located on the surface of each protein.
机译：哺乳动物端粒由与端粒DNA结合蛋白TRF1和TRF2相关的双链端粒TTAGGG重复序列组成。 TRF1和TRF2包含相似的C末端Myb结构域，可介导序列特异性结合端粒DNA。在发芽的酵母中，端粒DNA与scRap1p相关，scRap1p具有中央DNA结合结构域，该结构域包含两个通过长连接子连接的结构相关的Myb结构域，一个N端BRCT域和一个C端RCT域。最近，鉴定了人scRap1p直系同源物（hRap1），并显示其包含与scRap1p类似的BRCT域和RCT域。但是，hRap1在蛋白质的中心仅包含一个可识别的Myb基序。此外，尽管scRap1p直接结合端粒DNA，但hRap1没有DNA结合能力。相反，hRap1通过TRF2绑定到端粒。在这里，我们通过NMR确定了hRap1的Myb结构域的溶液结构。它包含由疏水核保持的三个螺旋。 hRap1 Myb域的体系结构非常接近TRF1，scRap1p和c-Myb中每个Myb域的体系结构。但是，hRap1 Myb结构域的静电势表面不同于其他Myb结构域的静电势表面。每个最小的DNA结合结构域，在TRF1中包含一个Myb结构域，在scRap1p和c-Myb中包含两个Myb结构域，表现出带正电的宽表面，该表面紧密接触DNA的带负电的主链。相比之下，hRap1 Myb结构域没有显示出明显的正表面，这说明其缺乏DNA结合活性。 hRap1 Myb结构域可能是第二类Myb基序的成员，后者缺乏DNA结合活性，但可能与其他蛋白质相互作用。此类的其他可能成员是c-Myb R1 Myb域以及ADA2和Adf1的Myb域。因此，尽管所有Myb结构域的折叠非常相似，但每个Myb结构域的功能取决于位于每种蛋白质表面的氨基酸残基。

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