Tétart F, Desplats C, Krisch H M
Laboratoire de Microbiologie et Génétique Moléculaire, CNRS, 118 Route de Narbonne, Toulouse Cedex, UPR 9007, France.
J Mol Biol. 1998 Sep 25;282(3):543-56. doi: 10.1006/jmbi.1998.2047.
The adsorption specificity of the T-even phages is determined by the protein sequence near the tip of the long tail fibers. These adhesin sequences are highly variable in both their sequence and specificity for bacterial receptors. The tail fiber adhesin domains are located in different genes in closely related phages of the T-even type. In phage T4, the adhesin sequence is encoded by the C-terminal domain of the large tail fiber gene (gene 37), but in T2, the adhesin is a separate gene product (gene 38) that binds to the tip of T2 tail fibers. Analysis of phage T6 and Ac3 sequences reveals additional variant forms of this locus. The tail fiber host specificity determinants can be exchanged, although the different loci have only limited homology. Chimeric fibers can be created by crossovers either between small homologies within the structural part of the fiber gene or in conserved motifs of the adhesin domain. For example, the T2 adhesin determinants are flanked by G-rich DNA motifs and exchanges involving these sequences can replace the specificity determinants. These features of the distal tail fiber loci genetically link their different forms and can mediate acquisition of diverse host range determinants, including those that allow it to cross species boundaries and infect taxonomically distant hosts.
T偶数噬菌体的吸附特异性由长尾纤维末端附近的蛋白质序列决定。这些粘附素序列在其序列和对细菌受体的特异性方面都高度可变。尾纤维粘附素结构域位于T偶数型密切相关噬菌体的不同基因中。在噬菌体T4中，粘附素序列由大尾纤维基因（基因37）的C末端结构域编码，但在T2中，粘附素是一种单独的基因产物（基因38），它与T2尾纤维的末端结合。对噬菌体T6和Ac3序列的分析揭示了该位点的其他变体形式。尾纤维宿主特异性决定簇可以交换，尽管不同的位点只有有限的同源性。嵌合纤维可以通过纤维基因结构部分内的小同源性之间或粘附素结构域的保守基序中的交叉来产生。例如，T2粘附素决定簇两侧是富含G的DNA基序，涉及这些序列的交换可以取代特异性决定簇。远端尾纤维位点的这些特征在遗传上连接了它们的不同形式，并可以介导多种宿主范围决定簇的获得，包括那些允许它跨越物种界限并感染分类学上遥远宿主的决定簇。
