Plasmid-encoded antirestriction protein ArdA can discriminate between type I methyltransferase and complete restriction-modification system
Plasmid-encoded antirestriction protein ArdA can discriminate between type I methyltransferase and complete restriction-modification system
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DOI：
10.1016/j.jmb.2006.09.087
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发表时间：
2007-01-12
影响因子：
5.6
通讯作者：
Belogurov, Anatol A.
中科院分区：
文献类型：
--
作者：
Nekrasov, Serge V.;Agafonova, Olga V.;Belogurov, Anatol A.
许多混杂质粒编码抗限制性蛋白ArdA（DNA限制的减轻），其特异性地影响大肠杆菌细胞中异源寡聚I型限制性修饰（R-M）系统的限制性活性。此外，许多推定的ardA基因编码的质粒和细菌染色体的全基因组序列的测序结果被发现，这表明ArdA蛋白和I型R-M系统，似乎是广泛存在于细菌中可能参与调控基因转移的细菌基因组。在这里，由IncI质粒ColIb-P9编码的ArdA的抗限制性作用的机制进行了研究，与充分研究的T7噬菌体编码的抗限制性蛋白OCR相比，使用突变分析，阻滞试验和His标签亲和层析。与Ocr一样，ArdA蛋白被证明能够有效地与EcoKI R-M复合物相互作用，并通过阻止其与特异性DNA的相互作用来影响其体内和体外限制活性。然而，与Ocr不同，ArdA蛋白对EcoKI Mtase具有低结合亲和力，并且ArdA需要额外的C-末端尾区（VF-运动）来有效地与I型R-M酶相互作用。似乎这种ArdA特征是其区分EcoKI MTase（修饰）和完整R-M系统（限制）的活性的能力的基础，所述完整R-M系统可以独立地与细胞中未修饰的DNA相互作用。这些研究结果表明，ArdA可以提供一个非常有效的和微妙的控制的限制和修改活动的I型系统和它的能力，以区别于DNA限制有利于特定的修改的DNA可能会给一些优势，有效地传输的ardA编码混杂质粒之间的不同的细菌种群。(c)2006爱思唯尔有限公司保留所有权利。
Many promiscuous plasmids encode the antirestriction proteins ArdA (alleviation of restriction of DNA) that specifically affect the restriction activity of heterooligomeric type I restriction-modification (R-M) systems in Escherichia coli cells. In addition, a lot of the putative ardA genes encoded by plasmids and bacterial chromosomes are found as a result of sequencing of complete genomic sequences, suggesting that ArdA proteins and type I R-M systems that seem to be widespread among bacteria may be involved in the regulation of gene transfer among bacterial genomes. Here, the mechanism of antirestriction action of ArdA encoded by IncI plasmid ColIb-P9 has been investigated in comparison with that of well-studied T7 phage-encoded antirestriction protein Ocr using the mutational analysis, retardation assay and His-tag affinity chromatography. Like Ocr, ArdA protein was shown to be able to efficiently interact with EcoKI R-M complex and affect its in vivo and in vitro restriction activity by preventing its interaction with specific DNA. However, unlike Ocr, ArdA protein has a low binding affinity to EcoKI Mtase and the additional C-terminal tail region (VF-motio is needed for ArdA to efficiently interact with the type I R-M enzymes. It seems likely that this ArdA feature is a basis for its ability to discriminate between activities of EcoKI Mtase (modification) and complete R-M system (restriction) which may interact with unmodified DNA in the cells independently. These findings suggest that ArdA may provide a very effective and delicate control for the restriction and modification activities of type I systems and its ability to discriminate against DNA restriction in favour of the specific modification of DNA may give some advantage for efficient transmission of the ardA-encoding promiscuous plasmids among different bacterial populations. (c) 2006 Elsevier Ltd. All rights reserved.