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首页> 外文期刊>Journal of Molecular Biology >Assemblies of replication initiator protein on symmetric and asymmetric DNA sequences depend on multiple protein oligomerization surfaces
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Assemblies of replication initiator protein on symmetric and asymmetric DNA sequences depend on multiple protein oligomerization surfaces

机译：复制起始蛋白在对称和不对称DNA序列上的组装取决于多个蛋白寡聚化表面

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摘要

The pi(35.0) protein of plasmid R6K regulates transcription and replication by binding a DNA sequence motif (TGAGR) arranged either asymmetrically into 22 bp direct repeats (DRs) in the gamma origin, or symmetrically into inverted half-repeats (IRs) in the operator of its own gene, pir. The binding patterns of the two natural forms of the pi protein and their heterodimers revealed that the predominant species, pi(35.0) (35.0 kDa), can bind to a single copy of the DR as either a monomer or a dimer while pi(30.5) (30.5 kDa) binds only as a dimer. We demonstrate that only one subunit of a pi(35.0) dimer makes specific contact with DNA. Electron microscopic (EM) analysis of the nucleoprotein complexes formed by pi(35.0) and DNA fragments containing all seven DRs revealed coupled ("hand-cuffed") DNA molecules that are aligned in a parallel orientation. Antiparallel orientations of the DNA were not observed. Thus, hand-cuffing depends on a highly ordered oligomerization of pi(35.0) in such structures. The pi protein (pi(35.0), pi(30.5)) binds to an IR as a dimer or heterodimer but not as a monomer. Moreover, a single amino acid residue substitution, F200S (pir200), introduced into pi(30.5) severely destabilizes dimers of this protein in solution and concomitantly prevents binding pf this protein to the IR. This mutation also changes the stability of pi(35.0) dimers but it does not change the ability of pi(35.0) to bind IRs. To explain these observations we propose that the diverse interactions of pi variants with DNA are controlled by multiple surfaces for protein oligomerization. (C) 1998 Academic Press. [References: 68]
机译：质粒R6K的pi（35.0）蛋白通过结合DNA序列基序（TGAGR）来调节转录和复制，该序列不对称地排列在γ起源的22 bp直接重复序列（DR）中，或对称地排列成反向的半重复序列（IR）。自己的基因pir的算子。两种天然形式的pi蛋白及其异二聚体的结合模式显示，主要物种pi（35.0）（35.0 kDa）可以结合DR的单个拷贝作为单体或二聚体，而pi（30.5 ）（30.5 kDa）仅作为二聚体结合。我们证明只有pi（35.0）二聚体的一个亚基才能与DNA发生特异性接触。由pi（35.0）和包含所有七个DR的DNA片段形成的核蛋白复合物的电子显微镜（EM）分析揭示了以平行方向排列的耦合（“手铐”）DNA分子。没有观察到DNA的反平行方向。因此，手铐取决于这种结构中pi（35.0）的高度有序的低聚。 pi蛋白（pi（35.0），pi（30.5））以二聚体或异二聚体而不是单体的形式与IR结合。此外，引入到pi（30.5）中的单个氨基酸残基取代F200S（pir200）严重破坏了该蛋白在溶液中的二聚体，并随之阻止了该蛋白与IR的结合。此突变也改变了pi（35.0）二聚体的稳定性，但没有改变pi（35.0）结合IR的能力。为了解释这些发现，我们建议pi变异体与DNA的各种相互作用受蛋白质寡聚化的多个表面控制。 （C）1998年学术出版社。 [参考：68]

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