Pratto Florencia, Cicek Aslan, Weihofen Wilhelm A, Lurz Rudi, Saenger Wolfram, Alonso Juan C
Department of Microbial Biotechnology, National Centre of Biotechnology, CSIC, 28049 Madrid, Spain.
Nucleic Acids Res. 2008 Jun;36(11):3676-89. doi: 10.1093/nar/gkn170. Epub 2008 May 13.
The accurate partitioning of Firmicute plasmid pSM19035 at cell division depends on ATP binding and hydrolysis by homodimeric ATPase delta(2) (ParA) and binding of omega(2) (ParB) to its cognate parS DNA. The 1.83 A resolution crystal structure of delta(2) in a complex with non-hydrolyzable ATPgammaS reveals a unique ParA dimer assembly that permits nucleotide exchange without requiring dissociation into monomers. In vitro, delta(2) had minimal ATPase activity in the absence of omega(2) and parS DNA. However, stoichiometric amounts of omega(2) and parS DNA stimulated the delta(2) ATPase activity and mediated plasmid pairing, whereas at high (4:1) omega(2) : delta(2) ratios, stimulation of the ATPase activity was reduced and delta(2) polymerized onto DNA. Stimulation of the delta(2) ATPase activity and its polymerization on DNA required ability of omega(2) to bind parS DNA and its N-terminus. In vivo experiments showed that delta(2) alone associated with the nucleoid, and in the presence of omega(2) and parS DNA, delta(2) oscillated between the nucleoid and the cell poles and formed spiral-like structures. Our studies indicate that the molar omega(2) : delta(2) ratio regulates the polymerization properties of (deltaATPMg(2+))(2) on and depolymerization from parS DNA, thereby controlling the temporal and spatial segregation of pSM19035 before cell division.
厚壁菌门质粒pSM19035在细胞分裂时的准确分配取决于同型二聚体ATP酶δ(2)(ParA)的ATP结合和水解,以及ω(2)(ParB)与其同源parS DNA的结合。δ(2)与不可水解的ATPγS复合物的1.83 Å分辨率晶体结构揭示了一种独特的ParA二聚体组装,其允许核苷酸交换而无需解离成单体。在体外,在没有ω(2)和parS DNA的情况下,δ(2)的ATP酶活性极低。然而,化学计量的ω(2)和parS DNA刺激了δ(2)的ATP酶活性并介导了质粒配对,而在高(4:1)ω(2):δ(2)比例下,ATP酶活性的刺激降低,并且δ(2)聚合到DNA上。δ(2)的ATP酶活性刺激及其在DNA上的聚合需要ω(2)结合parS DNA及其N端的能力。体内实验表明,单独的δ(2)与类核相关,并且在存在ω(2)和parS DNA的情况下,δ(2)在类核和细胞极之间振荡并形成螺旋状结构。我们的研究表明,摩尔ω(2):δ(2)比例调节(deltaATPMg(2+))(2)在parS DNA上的聚合特性及其从parS DNA上的解聚,从而在细胞分裂前控制pSM19035的时空分离。