Leong J M, Nunes-Düby S, Lesser C F, Youderian P, Susskind M M, Landy A
J Biol Chem. 1985 Apr 10;260(7):4468-77.
Although the lambdoid bacteriophage phi 80 and P22 possess site-specific recombination systems analogous to bacteriophage lambda, they have different attachment (att) site specificities. We have identified and determined the nucleotide sequences of the att sites of phi 80 and P22 and have examined the interaction of these sites with purified Escherichia coli integration host factor (IHF). The sizes of the homologous core regions of the att sites vary greatly: P22 has a 46-base pair core, while phi 80 and lambda have 17- and 15-base pair cores, respectively. The core sequences of the three phage show no significant homology, although dispersed regions of homology in arm sequences indicate that the three phage att sites are related. All three att sites have a high A + T composition, and restriction fragments carrying these sites migrate anomalously upon polyacrylamide gel electrophoresis. IHF binds to a site to the left of the common core in the phi 80 and P22 phage att sites (attP) and to a site to the right of the core in P22 attP and attB (the bacterial att site). In the lambda system, IHF interacts with three regions on attP (designated H1, H2, and H') and none on attB (Craig N., and Nash, H.A. (1984) Cell 39, 707-716). Alignment of the IHF sites of all three phage results in a consensus sequence for IHF binding, Pyr-AANNNNTTGATAT. Among the three phage, the number of IHF sites differs; however, the location and orientation of the binding sites in relation to the respective core regions are well conserved. An IHF site analogous to lambda H2 is present in both phi 80 and P22 attP, while a site analogous to lambda H' is present in P22 attP. This conservation suggests that IHF plays a very similar role in the site-specific recombination pathways of all three phage, and that the flanking arm sequences are necessary for phi 80 and P22 attP function, as is the case for lambda attP function. These structural similarities presumably reflect a conservation of the mechanism of site-specific recombination for the three phage.
尽管λ样噬菌体φ80和P22拥有与噬菌体λ类似的位点特异性重组系统，但它们具有不同的附着（att）位点特异性。我们已经鉴定并确定了φ80和P22的att位点的核苷酸序列，并研究了这些位点与纯化的大肠杆菌整合宿主因子（IHF）的相互作用。att位点同源核心区域的大小差异很大：P22有一个46个碱基对的核心，而φ80和λ分别有17个和15个碱基对的核心。尽管臂序列中的分散同源区域表明这三种噬菌体的att位点相关，但这三种噬菌体的核心序列没有明显的同源性。所有三个att位点都具有高A + T组成，并且携带这些位点的限制片段在聚丙烯酰胺凝胶电泳时迁移异常。IHF结合到φ80和P22噬菌体att位点（attP）中共同核心左侧的一个位点以及P22 attP和attB（细菌att位点）中核心右侧的一个位点。在λ系统中，IHF与attP上的三个区域（称为H1、H2和H'）相互作用，而与attB上的区域无相互作用（Craig N.和Nash，H.A.（1984年）《细胞》39卷，707 - 716页）。所有三种噬菌体的IHF位点比对产生了一个IHF结合的共有序列，即Pyr - AANNNNTTGATAT。在这三种噬菌体中，IHF位点的数量不同；然而，结合位点相对于各自核心区域的位置和方向是高度保守的。类似于λ H2的一个IHF位点存在于φ80和P22的attP中，而类似于λ H'的一个位点存在于P22的attP中。这种保守性表明IHF在所有三种噬菌体的位点特异性重组途径中发挥非常相似的作用，并且侧翼臂序列对于φ80和P22的attP功能是必需的，就像对于λ attP功能一样。这些结构相似性大概反映了这三种噬菌体位点特异性重组机制的保守性。
