Histone-like proteins and bacterial chromosome structure.
Histone-like proteins and bacterial chromosome structure.
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DOI：
10.1016/s0021-9258(18)37625-7
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发表时间：
1988-09
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影响因子：
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通讯作者：
David E. Pettijohn
中科院分区：
文献类型：
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作者：
David E. Pettijohn
前体细胞合成一组结合DNA的小的、通常为碱性的蛋白质，由于它们的生物化学性质类似于真核生物的组蛋白，因此统称为组蛋白样蛋白。真核生物组蛋白通过抑制核小体中的左旋环形DNA超螺旋来包装DNA，而原核生物组蛋白样蛋白的功能尚不清楚。然而，最近对某些组蛋白样蛋白与DNA的相互作用的研究以及对编码这些蛋白质的基因突变的细胞的遗传学研究开始表明某些蛋白质的功能。这些发现和原核染色体结构的关系将在这里简要回顾。此时，五种不同类型的细菌蛋白被认为是组蛋白样的。这些措施包括：（1）HU蛋白（综述参见Drlica和Rouviere-Yaniv，1987），它是一种小的二聚体蛋白，在大肠杆菌中由分别命名为HU-α和HU-8的M亚基9，535和9，225组成，也分别称为HU-2和HU-1，并由基因hupA和hupB编码，分别（许多其他细菌物种只有单一基因和单一类型的HU亚基）; 2）整合宿主因子（IHF）（Nash和Robertson，1981），一种基本上与HU具有氨基酸序列同源性的碱性蛋白，显然由两个亚基IHF-α和IHF-β组成，具有M，11，224和10，581，并由E. coli基因himA和hip; 3）蛋白H1（Spassky等，1984），一种以三种不同形式Hla、Hlb和Hlc存在的中性蛋白，具有不同的等电点，但具有相同的M，15，500; 4）HLP 1（Lathe等人，1980），一种蛋白质M，17,000，这显然是产品的E。coli firA基因; 5）蛋白H（Hubscher等，1980）的M，28，000，与真核组蛋白H2 A特异性抗体交叉反应。此外，噬菌体可以编码与HU蛋白具有同源性的特定蛋白质（格林等人，1984），并且可以产生与宿主细胞HU偶联的蛋白质，并明显地在功能上修饰它。2这些组蛋白样蛋白在大肠杆菌中均具有较高的胞内浓度，大肠杆菌的范围从最丰富的H和HU（每个细胞分别约120，000和60，000个单体）到最不丰富的H1和IHF（估计每个指数生长细胞约14，000至20，000个拷贝或更少）。必须认识到，某些丰度数字可能被低估，因为它们是根据纯化后的回收量计算的。HU蛋白是研究最彻底的蛋白，在不同的原核生物中高度保守，存在于真细菌、古细菌、蓝绿色细菌、细菌和细菌中。
Prokaryotic cells synthesize a set of small, usually basic proteins that bind DNA and are collectively called histonelike proteins because their biochemical properties resemble eukaryotic histones. Whereas the eukaryotic histones have a well defined function in packaging DNA through restraining left-handed toroidal DNA supercoils in nucleosomes, the functions of the prokaryotic histone-like proteins are not yet clear. However, recent studies of the interactions of certain histone-like proteins with DNA and genetic studies of cells that are mutated in genes coding for these proteins are beginning to suggest functions for some of the proteins. These findings and the relations to prokaryotic chromosome structure will be briefly reviewed here. At this time five different types of bacterial proteins are considered to be histone-like. These include: 1) the HU protein (for review see Drlica and Rouviere-Yaniv, 1987), which is a small dimeric protein that in Escherichia coli is composed of subunits of M, 9,535 and 9,225 named HU-a and HU-8, respectively, also called HU-2 and HU-1, respectively, and coded by the genes hupA and hupB, respectively (many other bacterial species have only a single gene and a single type of HU subunit); 2) integration host factor (IHF)'(Nash and Robertson, 1981), a basic protein having substantial amino acid sequence homology with HU, apparently composed of two subunits IHF-a and IHF-@, having M, 11,224 and 10,581, respectively, and coded by the E. coli genes himA and hip, respectively; 3) protein H1 (Spassky et al., 1984), a neutral protein existing in three different forms Hla, Hlb, and Hlc having different isoelectric points, but the same M, 15,500; 4) HLPl (Lathe et al., 1980), a protein of M, 17,000, which is apparently the product of the E. coli firA gene; 5) protein H (Hubscher et al., 1980) of M, 28,000, cross-reacting with antibodies specific for eukaryotic histone H2A. Also, bacteriophages can code for specific proteins having homology to HU protein (Greene et al., 1984) and can make proteins that couple to host cell HU and apparently modify it functionally. 2 Each of these histone-like proteins has a relatively high intracellular concentration, which in E. coli ranges from that of H and HU which are the most abundant, roughly 120,000 and 60,000 monomers per cell, respectively, to the least abundant H1 and IHF estimated at about 14,000 to 20,000 copies or less per exponentially growing cell. It is important to recognize that some of the figures for abundance could be underestimated, since they are calculated from recoveries after purification. The HU proteins, which are the most thoroughly studied, are highly conserved in different prokaryotes and are found in eubacteria, archaebacteria, blue-green