Cai Z, Gorin A, Frederick R, Ye X, Hu W, Majumdar A, Kettani A, Patel D J
Cellular Biochemistry and Biophysics Program Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Nat Struct Biol. 1998 Mar;5(3):203-12. doi: 10.1038/nsb0398-203.
We have determined the solution structure of a 15-mer boxB RNA hairpin complexed with a 20-mer basic peptide of the N protein involved in bacteriophage P22 transcriptional antitermination. Complex formation involves adaptive binding with the N peptide adopting a bent alpha-helical conformation that packs tightly through hydrophobic and electrostatic interactions against the major groove face of the boxB RNA hairpin, orienting the open opposite face for potential interactions with host factors and/or RNA polymerase. Four nucleotides in the boxB RNA hairpin pentaloop form a stable GNRA like tetraloop structural scaffold on complex formation, allowing the looped out fifth nucleotide to make extensive hydrophobic contacts with the bound peptide. The guanidinium group of a key arginine is hydrogen-bonded to the guanine in a loop-closing sheared G.A mismatch and to adjacent backbone phosphates. The identified intermolecular contacts account for the consequences of N peptide and boxB RNA mutations on bacteriophage transcriptional antitermination.
我们已经确定了一个与参与噬菌体P22转录抗终止作用的N蛋白的20聚体碱性肽复合的15聚体boxB RNA发夹的溶液结构。复合物的形成涉及适应性结合，N肽采用弯曲的α-螺旋构象，通过疏水和静电相互作用紧密堆积在boxB RNA发夹的大沟面上，使开放的相对面定向，以便与宿主因子和/或RNA聚合酶进行潜在的相互作用。boxB RNA发夹五碱基环中的四个核苷酸在复合物形成时形成稳定的类似GNRA的四环结构支架，使环出的第五个核苷酸与结合的肽进行广泛的疏水接触。一个关键精氨酸的胍基与环闭合剪切G·A错配中的鸟嘌呤以及相邻的主链磷酸基团形成氢键。所确定的分子间接触解释了N肽和boxB RNA突变对噬菌体转录抗终止的影响。
