One-way ticket to the cell pole: plasmid transport by the prokaryotic tubulin homolog TubZ.
One-way ticket to the cell pole: plasmid transport by the prokaryotic tubulin homolog TubZ.
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通往细胞极的单程票：通过原核微管蛋白同系物 TubZ 进行质粒运输。
DOI：
10.1073/pnas.1007331107
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发表时间：
2010
影响因子：
11.1
通讯作者：
Barillà D
中科院分区：
文献类型：
--
作者：
Barillà D
每个细胞在其生命周期中都面临着许多挑战。其中最关键的一项是确保其基因遗产准确地传递给子代细胞。在细菌中，最仔细剖析的DNA分离机制是那些由低拷贝数质粒指定的机制。高拷贝数质粒在细胞分裂时的分布依赖于被动扩散，而低拷贝数质粒则需要特殊的机制。这个工具包由一个特殊的分离位点决定，由三个基本成分组成：(I)编码具有ATP或GTP结合基序的聚合马达蛋白的基因，(Ii)编码DNA结合蛋白的基因，以及(Iii)位于这两个基因上游或下游的顺式着丝粒样位点。根据分配盒的遗传组织和编码蛋白(1-4)之间的系统发育关系，分离基因被划分为三大类(I-III型)。I型系统包括Walker型ATPase，表示为Para：它们是最广泛的分离模块，由低拷贝数质粒和许多细菌和古生物染色体上的分割盒编码(5)。类型II模块编码一个NTPase，Parm，它是真核细胞肌动蛋白的祖先同源物(6)。虽然在进化上不相关，但Parm和Parm蛋白都是基于聚合的引擎，它们组装成细胞骨架结构，参与DNA的运输、定位和分离(3，4)。III型系统最近被发现：这一发现为原核生物细胞骨架蛋白调节基因组分离开辟了不可预见的前景(7-9)。在PNAS中，Ni等人。通过报道苏云金芽孢杆菌pBtoxis质粒编码的TubR和TubZ蛋白的结构，阐明了支持III型分配盒功能的分子机制(10)。在蜡状芽孢杆菌细菌组(7，9)的大质粒上发现了III型分离模块。质粒pBtoxis的分隔盒含有两个基因：orf157编码11.6 kDa的特异性DNA结合蛋白，称为Tubr，orf156编码54.4 kDa
Each cell faces many challenges during its life cycle. One of the most crucial is ensuring that its genetic patrimony is accurately passed on to daughter cells. In bacteria, the most well-dissected DNA segregation mechanisms are those specified by lowcopy-number plasmids. Whereas highcopy-number plasmids rely on passive diffusion for their distribution at cell division, low-copy-number plasmids require specialized mechanisms. To this end, they encode a “survival tool kit” enabling them to be delivered to and partitioned into daughter cells.This tool kit is specified by a dedicated segregation locus, consisting of three essential components:(i) a gene encoding a polymerizing motor protein with an ATP-or GTP-binding motif,(ii) a gene encoding a DNA-binding protein, and (iii) a cis-acting centromere-like site, located either upstream or downstream of the two genes. Segregation loci have been assigned to three main categories (types I–III) on the basis of the genetic organization of the partition cassette and the phylogenetic relationships among the encoded proteins (1–4). Type I systems include a Walkertype ATPase, denoted as ParA: they are the most widespread segregation modules and are encoded by partition cassettes found on low-copy-number plasmids and on many bacterial and archaeal chromosomes (5). Type II modules encode a NTPase, ParM, which is an ancestral homolog of eukaryotic actin (6). Although evolutionarily unrelated, both ParA and ParM proteins are polymerization-based engines that assemble into cytoskeletal structures involved in DNA transport, positioning, and segregation (3, 4). Type III systems were identified more recently: this discovery has opened up unforeseen perspectives on prokaryotic cytoskeletal proteins mediating genome segregation (7–9). In PNAS, Ni et al. shed light on the molecular mechanisms underpinning the function of type III partition cassettes by reporting the structures of TubR and TubZ proteins encoded by the pBtoxis plasmid from Bacillus thuringiensis (10). Type III segregation modules are found on large plasmids of the Bacillus cereus group of bacteria (7, 9). The partition cassette of plasmid pBtoxis harbors two genes: orf157 encoding an 11.6-kDa specific DNA-binding protein, known as TubR, and orf156 encoding a 54.4-kDa