PHAGE T4 HEAD ASSEMBLY AND INITIATION OF INFECTION

研究的重点是病毒DNA包装的机制 并对噬菌体T4体外包装衍生的构建进行了研究 克隆载体。 我们的工作特别针对1） 了解多功能的结构和功能 噬菌体T4包装（前头部和末端酶）蛋白。 第三个- 酶促（DNA易位）和 主要衣壳的结构（前头部形状决定）作用 蛋白质gp 23 *），少量加工的酶产物（gp 23 **）， 和衣壳基因突变体的数量将被确定。 大会 DNA入口（也是头端起始）顶点作为 将使用过表达来检查整合膜蛋白 载体;催化基因产物和宿主系统在 将确定膜插入。 特定包装 将选择这两种前头蛋白中的突变 在基因定向诱变之后。 DNA末端酶 与DNA入口顶点蛋白相互作用的蛋白质， 该探针已经过表达和纯化--它们 DNA易位和多联体的作用机制 切割将被调查。 λ和λ-pBR 322 衍生DNA可以在体外包装到T4头部中。 cos 和/或P1 DNA包装到T4中，并与 同源位点特异性重组系统应该允许 T4-杂合巨噬细胞载体的开发。 我们提出 一种新的噬菌体DNA螺旋折叠模型。 形态学和（与噬菌体）化学工作可以明确地 建立这个模型。 包装的扭结或非B型DNA将 检测到，其与DNA结合位点的相互作用， 主要衣壳蛋白及其次要加工酶产物 (gp23**）将被探测。 我们将确定哪些DNA结构 可以在体内和体外包装;例如， 异源双链体环在体外从包装的DNA中排除，并且 终止酶蛋白是否起区别这种 在DNA修复过程中的作用。

The research focuses on the mechanism of viral DNA packaging and on the construction of phage T4 in vitro packaging-derived cloning vectors. Our work is especially directed toward 1) understanding the structures and functions of the multifunctional phage T4 packaging (prohead and terminase) proteins. The 3- dimensional basis for enzymatic (DNA translocating) and structural (prohead form-determining) roles of the major capsid protein gp23*), of a minor processed enzymatic product (gp23**), and of capsid gene mutants will be determined. The assembly of the DNA entrance (also the prohead initiation) vertex as an integral membrane protein will be examined using overexpression vectors; the role of a catalytic gene product and host systems in the membrane insertion will be determined. Specific packaging mutations in both these prohead proteins will be selected following gene-directed mutagenesis. The DNA terminase proteins which interact with the DNA entrance vertex protein in the prohead have been overexpressed and purified-their mechanisms of action in DNA translocation and concatemer cutting will be investigated. lambda and lambda-pBR322 derivative DNAs can be packaged into T4 heads in vitro. cos and/or P1 DNAs packaged into T4 and recircularized with the homologous site-specific recombination systems should allow development of T4-hybrid megacosmid vectors. We have proposed a novel "spiral-fold" model for packaged phage DNA. Morphological and (with phage ) chemical work can definitively establish this model. Packaged kinked or non-B form DNA will be detected, and its interaction with the DNA binding site in the major capsid protein and its minor processed enzymatic product (gp23**) will be probed. We will determine what DNA structures can be packaged in vivo and in vitro; e.g. whether nicks and heteroduplex loops are excluded from packaged DNA in vitro, and whether the terminase proteins act to discriminate against such structures in coupled DNA repair processes.