Nature Communications 2022
a Surface representation of composite cryo-EM map of virion of phage SU10 colored according to protein type. The major capsid protein (gp9) is shown in turquoise, portal protein (gp6) in magenta, adaptor protein (gp11) in yellow, long tail fibers (gp12) in violet, nozzle protein (gp17) in red, short tail fibers (gp16) in green, and tail needle (gp18) in light blue. The length of the virion is 1590 Å. For details on the construction of the composite map, please see the Materials and methods section. b The same as A, but the front half of the composite map of the SU10 head was removed to show the structure of the genome in grey. The inset shows a 2D class average of the SU10 virion. The scale bar indicates 45 nm. c Composite cryo-EM map of portal and tail complexes of SU10 virion. The length of the complex is 540 Å. d Cryo-EM reconstruction of portal and tail complexes from an SU10 genome release intermediate. e Composite cryo-EM map of genome-release intermediate of SU10. The front half of the head was removed to show the structure of the genome remaining in the capsid. The inset shows a 2D class average of the SU10 genome release intermediate. f Schematic representation of segment of SU10 genome encoding structural proteins color-coded the same as the proteins in panels a to e. Proteins shown in white are either non-structural or were not identified in the reconstructions.
Significance
Escherichia coli phage SU10 belongs to the genus Kuravirus from the class Caudoviricetes of phages with short non-contractile tails. In contrast to other short-tailed phages, the tails of Kuraviruses elongate upon cell attachment. Here we show that the virion of SU10 has a prolate head, containing genome and ejection proteins, and a tail, which is formed of portal, adaptor, nozzle, and tail needle proteins and decorated with long and short fibers. The binding of the long tail fibers to the receptors in the outer bacterial membrane induces the straightening of nozzle proteins and rotation of short tail fibers. After the re-arrangement, the nozzle proteins and short tail fibers alternate to form a nozzle that extends the tail by 28 nm. Subsequently, the tail needle detaches from the nozzle proteins and five types of ejection proteins are released from the SU10 head. The nozzle with the putative extension formed by the ejection proteins enables the delivery of the SU10 genome into the bacterial cytoplasm. It is likely that this mechanism of genome delivery, involving the formation of the tail nozzle, is employed by all Kuraviruses.
Šiborová, M., Füzik, T., Procházková,M., Nováček, J., Benešík, M., Nilsson, A.S., and Plevka, P.:
Tail proteins of phage SU10 reorganize into the nozzle for genome delivery, Nature Comm. (2022)13:5622,https://doi.org/10.1038/s41467-022-33305-w