BACTERIOPHAGE-P22 PORTAL PROTEIN IS PART OF THE GAUGE THAT REGULATES PACKING DENSITY OF INTRAVIRION DNA
BACTERIOPHAGE-P22 PORTAL PROTEIN IS PART OF THE GAUGE THAT REGULATES PACKING DENSITY OF INTRAVIRION DNA
复制标题
DOI：
10.1016/0022-2836(92)90469-z
复制
发表时间：
1992-04-20
影响因子：
5.6
通讯作者：
SERWER, P
中科院分区：
文献类型：
--
作者：
CASJENS, S;WYCKOFF, E;SERWER, P
复杂的双链DNA噬菌体组装无DNA的蛋白质外壳（原壳），随后包装DNA。在包括P22在内的几种双链DNA噬菌体的情况下，包装与从复制产生的串联分子中切割DNA有关。成熟的病毒内粒子P22 DNA具有非唯一（环状排列）的末端和由原衣壳决定的长度。在所有已知的情况下，原衣壳由一个外壳蛋白，一个内部支架蛋白（协助外壳蛋白壳的组装）和一个由12个相同的门脉蛋白亚基组成的环组成，DNA可以通过这个环进入原衣壳。为了研究门脉蛋白在从串联体切割排列DNA中的作用，我们对P22门脉蛋白突变体进行了表征。P22门脉蛋白中几个单氨基酸的变化对被包装DNA的长度、DNA在病毒粒子内凝聚的密度和衣壳的外半径的影响已经被确定。一个突变体（NT5/1a）的结果表明，衣壳半径没有变化（±0.5%），但成熟DNA比野生型P22长4.7%，包装密度也相应提高。因此，门脉蛋白是调节噬菌体P22中DNA长度和包装密度的标准的一部分。我们认为，这些发现使DNA包装模型不太可能在包装密度是一个性质单独的外壳蛋白壳或DNA本身。
The complex double-stranded DNA bacteriophages assemble DNA-free protein shells (procapsids) that subsequently package DNA. In the case of several double-stranded DNA bacteriophages, including P22, packaging is associated with cutting of DNA from the concatemeric molecule that results from replication. The mature intravirion P22 DNA has both non-unique (circularly permuted) ends and a length that is determined by the procapsid. In all known cases, procapsids consist of an outer coat protein, an interior scaffolding protein that assists in the assembly of the coat protein shell, and a ring of 12 identical portal protein subunits through which the DNA is presumed to enter the procapsid. To investigate the role of the portal protein in cutting permuted DNA from concatemers, we have characterized P22 portal protein mutants. The effects of several single amino acid changes in the P22 portal protein on the length of the DNA packaged, the density to which DNA is condensed within the virion, and the outer radius of the capsid have been determined. The results obtained with one mutant (NT5/1a) indicate no change (±0·5%) in the radius of the capsid, but mature DNA that is 4·7% longer and a packing density that is commensurately higher than those of wild-type P22. Thus, the portal protein is part of the gauge that regulates the length and packaging density of DNA in bacteriophage P22. We argue that these findings make models for DNA packaging less likely in which the packing density is a property solely of the coat protein shell or of the DNA itself.