6yt5
Cryo-EM structure of T7 bacteriophage DNA translocation gp15-gp16 core complex intermediate assembly
Structural highlights
FunctionGP15_BPT7 Component of the cylindrical core that assembles on the inner surface of the capsid during capsid formation and plays a role in viral DNA ejection into the host cell. The inner core is composed of stacked rings of gp14, gp15 and gp16 proteins. Following binding to the host cell surface, the internal core is disassembled and gp15 is ejected along with gp14 and gp16 into the infected cell. Gp15 probably remains associated with gp16. The gp15-gp16 complex binds to both the viral DNA and the host inner membrane, probably escorting the leading end of the genome through the periplasm and controlling the extend of DNA translocated into the host cell.[HAMAP-Rule:MF_04122][1] [2] Publication Abstract from PubMedIn most bacteriophages, genome transport across bacterial envelopes is carried out by the tail machinery. In viruses of the Podoviridae family, in which the tail is not long enough to traverse the bacterial wall, it has been postulated that viral core proteins assembled inside the viral head are translocated and reassembled into a tube within the periplasm that extends the tail channel. Bacteriophage T7 infects Escherichia coli, and despite extensive studies, the precise mechanism by which its genome is translocated remains unknown. Using cryo-electron microscopy, we have resolved the structure of two different assemblies of the T7 DNA translocation complex composed of the core proteins gp15 and gp16. Gp15 alone forms a partially folded hexamer, which is further assembled upon interaction with gp16 into a tubular structure, forming a channel that could allow DNA passage. The structure of the gp15-gp16 complex also shows the location within gp16 of a canonical transglycosylase motif involved in the degradation of the bacterial peptidoglycan layer. This complex docks well in the tail extension structure found in the periplasm of T7-infected bacteria and matches the sixfold symmetry of the phage tail. In such cases, gp15 and gp16 that are initially present in the T7 capsid eightfold-symmetric core would change their oligomeric state upon reassembly in the periplasm. Altogether, these results allow us to propose a model for the assembly of the core translocation complex in the periplasm, which furthers understanding of the molecular mechanism involved in the release of T7 viral DNA into the bacterial cytoplasm. Assisted assembly of bacteriophage T7 core components for genome translocation across the bacterial envelope.,Perez-Ruiz M, Pulido-Cid M, Luque-Ortega JR, Valpuesta JM, Cuervo A, Carrascosa JL Proc Natl Acad Sci U S A. 2021 Aug 24;118(34). pii: 2026719118. doi:, 10.1073/pnas.2026719118. PMID:34417311[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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