SUBUNIT-SPECIFIC PHENOTYPES OF SALMONELLA-TYPHIMURIUM HU MUTANTS
SUBUNIT-SPECIFIC PHENOTYPES OF SALMONELLA-TYPHIMURIUM HU MUTANTS
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DOI：
10.1128/jb.172.9.5402-5407.1990
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发表时间：
1990-09-01
影响因子：
3.2
通讯作者：
HIGGINS, NP
中科院分区：
文献类型：
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作者：
HILLYARD, DR;EDLUND, M;HIGGINS, NP
研究了沙门氏菌 hupA 和 hupB 突变体，以确定细菌中 HU 结构高度保守的原因。我们发现了一种 HU-1 特有的效应；与 hupA 或野生型细胞相比，F''128 质粒在 hupB 中的稳定性低 25 倍。与野生型细胞相比，hupA hupB 双突变体中的 F'' 质粒不稳定 120 倍，并且双突变体的质粒 DNA 结构也发生了显着改变。与野生型细胞相比，从 hupA hupB 菌株中分离出的 pBR322 DNA 超螺旋缺陷为 10% 至 15%，并且拓扑异构体分布比野生型或单一突变菌株显着更加异质。 HU 失活改变的其他系统包括鞭毛相位变化和噬菌体 Mu 转座。然而，沙门氏菌 HU 双突变体中的 Mu 转座率仅低四倍左右。与大肠杆菌相比，沙门氏菌 HU 双突变体的 MU 转座缺陷可能较少，原因之一是双突变体中合成了一种新的、小的、碱性热稳定蛋白，该蛋白可能部分补偿 HU 的损失。结果表明，尽管单独的 HU-1 或 HU-2 亚基可以满足一般染色体组织的细胞需求，但在进化过程中保存 HU-1 和 HU-2 结构的选择压力可能涉及各个亚基的特殊作用。
Salmonella hupA and hupB mutants were studied to determine the reasons for the high degree of conservation in HU structure in bacteria. We found one HU-1-specific effect; the F''128 plasmid was 25-fold less stable in hupB compared with hupA or wild-type cells. F'' plasmids were 120-fold more unstable in hupA hupB double mutants compared with wild-type cells, and the double mutant also had a significant alteration in plasid DNA structure. pBR322 DNA isolated from hupA hupB strains was deficient in supercoiling by 10 to 15% compared with wild-type cells, and the topoisomer distribution was significantly more heterogeneous than in wild-type or single-mutant strains. Other systems altered by HU inactivation included flagellar phase variation and phage Mu transposition. However, Mu transposition rates were only about fourfold lower in Salmonella HU double mutants. One reason that Salmonella HU double mutants may be less defective for MU transposition than Escherichia coli is the synthesis in double mutants of a new, small, basic heat-stable protein, which might partially compensate for the loss of HU. The results indicate that although either HU-1 or HU-2 subunit alone may accommodate the cellular need for general chromosomal organization, the selective pressure to conserve HU-1 and HU-2 structure during evolution could involve specialized roles of the individual subunits.