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Publication Abstract from PubMed

Bacteriophages of Borrelia burgdorferi are a biologically important but under-investigated feature of the Lyme disease-causing spirochete. No virulent borrelial viruses have been identified, but all B. burgdorferi isolates carry a prophage phiBB1 as resident circular plasmids. Like its host, the phiBB1 phage is quite distinctive and shares little sequence similarity with other known bacteriophages. We expressed phiBB1 head morphogenesis proteins in Escherichia coli which resulted in assembly of homogeneous prolate procapsid structures and used cryo-electron microscopy to determine the three-dimensional structure of these particles. The phiBB1 procapsids consist of 415 copies of the major capsid protein and an equal combined number of three homologous capsid decoration proteins that form trimeric knobs on the outside of the particle. One of the end vertices of the particle is occupied by a portal assembled from twelve copies of the portal protein. The phiBB1 scaffolding protein is entirely alpha-helical and has an elongated shape with a small globular domain in the middle. Within the tubular section of the procapsid, the internal scaffold is built of stacked rings, each composed of 32 scaffolding protein molecules, which run in opposite directions from both caps with a heterogeneous part in the middle. Inside the portal-containing cap, the scaffold is organized asymmetrically with ten scaffolding protein molecules bound to the portal. The phiBB1 procapsid structure provides better insight into the vast structural diversity of bacteriophages and presents clues of how elongated bacteriophage particles might be assembled.

Structure of the Borrelia Bacteriophage phiBB1 Procapsid.,Rumnieks J, Fuzik T, Tars K J Mol Biol. 2023 Dec 15;435(24):168323. doi: 10.1016/j.jmb.2023.168323. Epub 2023 , Oct 20. PMID:37866476^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.