Cryo- EM structure of cyanopodophage A4 reveals a pentameric pre- ejectosome in the double- stabilized capsid

• 成果类型: Article
• 署名作者: Hou, Pu; Zhou, Rui-Qian; Jiang, Yong-Liang; Yu, Rong-Cheng; Du, Kang; Gan, Nanqin; Ke, Fei; Zhang, Qi-Ya; Li, Qiong; Zhou, Cong-Zhao
• 署名单位: Chinese Academy of Sciences; University of Science & Technology of China, CAS; Chinese Academy of Sciences; University of Science & Technology of China, CAS; Chinese Academy of Sciences; University of Science & Technology of China, CAS; Chinese Academy of Sciences; Institute of Hydrobiology, CAS
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11747
• DOI: 10.1073/pnas.2423403122
• 发表日期: 2025-04-08
• 关键词: bacteriophage t7; phage t7; protein; dna; genome; Visualization; maturation; symmetry; release; motion

摘要

Upon infection, the podophages usually eject a couple of proteins from the capsid to form a transmembrane ejectosome on the host cell membrane that facilitates the ejection of viral genome. However, it remains unclear how these proteins of pre-ejectosome are finely assembled at the center of highly packaged genome. Here, we report the intact structure of Anabaena cyanopodophage A4, which consists of a capsid stabilized by two types of cement proteins and a short tail attached with six tail fibers. Notably, we find a pentameric pre-ejectosome at the core of capsid, which is composed of four ejection proteins wrapped into a coaxial cylinder of triple layers. Moreover, a segment of genomic DNA runs along the positively charged circular cleft formed by two ejection proteins. Based on the mortise-and-tenon architecture of pre-ejectosome in combination with previous studies, we propose a putative DNA packaging process and ejection mechanism for podophages. These findings largely enrich our knowledge on the assembly mechanism of podophages, which might facilitate the application of A4 as a chassis cyanophage in synthetic biology.