Cabral Julia Elise, Qiu Yanfei, Heck Albert J R, McNulty Reginald
Laboratory of Macromolecular Structure, Department of Molecular Biology and Biochemistry, University of California Irvine, Steinhaus Hall, Irvine, CA 92697-3900, USA.
Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Netherlands Proteomics Center, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Pathogens. 2024 Dec 3;13(12):1066. doi: 10.3390/pathogens13121066.
Concatemeric viral DNA is packaged into bacteriophage P22 procapsids via a headful packaging mechanism mediated by a molecular machine consisting of small (gp3) and large (gp2) terminase subunits. Although a negative stain reconstruction exists for the terminase holoenzyme, it is not clear how this complex binds the dodecameric portal protein located at a 5-fold mismatch vertex. Herein, we describe new assemblies for the holoenzyme. Both native mass spectrometry and transmission electron microscopy reveal that the P22 terminase complex adopts three main assemblies, which include a nonameric S-terminase bound to two L-terminase 1(gp3):2(gp2), two nonameric S-terminase bound to five L-terminase 2(gp3):5(gp2), and three nonameric S-terminase bound to seven L-terminase 3(gp3):7(gp2). Native agarose gel electrophoresis shows that the terminase complex interacts with procapsids with mild crosslinking. These results herein illustrate the P22 terminase complex can adopt a variety of conformations and assembly states.
串联体病毒DNA通过一种由小（gp3）和大（gp2）末端酶亚基组成的分子机器介导的“满头部”包装机制被包装进噬菌体P22原衣壳中。尽管存在末端酶全酶的负染重建结构，但尚不清楚该复合物如何结合位于五重错配顶点的十二聚体门户蛋白。在此，我们描述了全酶的新组装形式。天然质谱和透射电子显微镜均显示，P22末端酶复合物呈现三种主要组装形式，包括与两个L末端酶1（gp3）:2（gp2）结合的九聚体S末端酶、与五个L末端酶2（gp3）:5（gp2）结合的两个九聚体S末端酶，以及与七个L末端酶3（gp3）:7（gp2）结合的三个九聚体S末端酶。天然琼脂糖凝胶电泳表明，末端酶复合物通过轻度交联与原衣壳相互作用。本文的这些结果表明，P22末端酶复合物可以呈现多种构象和组装状态。
