Structural analysis of the chromosome segregation protein Spo0J from Thermus thermophilus
Structural analysis of the chromosome segregation protein Spo0J from Thermus thermophilus
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DOI：
10.1111/j.1365-2958.2004.04133.x
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发表时间：
2004-07-01
影响因子：
3.6
通讯作者：
Löwe, J
中科院分区：
文献类型：
--
作者：
Leonard, TA;Butler, PJG;Löwe, J
原核生物的染色体和质粒编码细胞分裂时DNA分离所需要的分裂系统。质粒分配位点编码两个蛋白，ParA和ParB，以及一个顺式作用的着丝粒样位点parS。ParA和ParB的染色体编码同源物Soj和Spo0J在细菌细胞分裂和产孢过程中对染色体分离起积极作用。Spo0J是一种dna结合蛋白，在体内与parS位点结合。利用多波长异常色散，对c端截断的Spo0J（氨基酸1-222）的x射线晶体结构进行了求解。它是一种dna结合蛋白，结构类似于抑制因子dna结合域的螺旋-转-螺旋（HTH）基序。晶体结构为反平行二聚体，每个单体的HTH基序的识别α -螺旋间距为34埃，与B-DNA的螺旋重复序列长度相对应。沉降速度和平衡超离心研究表明，全长Spo0J在溶液中以单体-二聚体平衡存在，Spo0J1-222为纯单体。Spo0J的c端结构域的沉积表明它完全是二聚体，证实了c端是主要的二聚结构域。我们假设c端介导Spo0J的二聚化，从而有效地增加了n端的局部浓度，正如我们的结构所示，n端很可能在与同源parS位点结合时发生二聚化。
Prokaryotic chromosomes and plasmids encode partitioning systems that are required for DNA segregation at cell division. The plasmid partitioning loci encode two proteins, ParA and ParB, and a cis-acting centromere-like site denoted parS. The chromosomally encoded homologues of ParA and ParB, Soj and Spo0J, play an active role in chromosome segregation during bacterial cell division and sporulation. Spo0J is a DNA-binding protein that binds to parS sites in vivo. We have solved the X-ray crystal structure of a C-terminally truncated Spo0J (amino acids 1-222) from Thermus thermophilus to 2.3 Angstrom resolution by multiwavelength anomalous dispersion. It is a DNA-binding protein with structural similarity to the helix-turn-helix (HTH) motif of the lambda repressor DNA-binding domain. The crystal structure is an antiparallel dimer with the recognition alpha-helices of the HTH motifs of each monomer separated by a distance of 34 Angstrom corresponding to the length of the helical repeat of B-DNA. Sedimentation velocity and equilibrium ultracentrifugation studies show that full-length Spo0J exists in a monomer-dimer equilibrium in solution and that Spo0J1-222 is exclusively monomeric. Sedimentation of the C-terminal domain of Spo0J shows it to be exclusively dimeric, confirming that the C-terminus is the primary dimerization domain. We hypothesize that the C-terminus mediates dimerization of Spo0J, thereby effectively increasing the local concentration of the N-termini, which most probably dimerize, as shown by our structure, upon binding to a cognate parS site.