Study details structural and functional aspects of ΦcrAss001, a prevalent human gut virus

Researchers looked into the structure and functionality of the abundant gut virus ΦcrAss001, studying its role in the human microbiome. The study by Oliver Bayfield, Andrey Shkoporov and several others was published on May 3.

According to the study, the recent discovery of crAssphage and related crassviruses, primarily identified through metagenomic sequencing, has enhanced our understanding of the human gut virome. These viruses, the study states, constituting a substantial portion of viral sequences in many individuals, are believed to play a crucial role in influencing the human microbiome's composition and functionality. However, until now, the specific structures and roles of many virally encoded proteins remained largely unidentified, with only basic bioinformatic predictions available, the study says.

The study utilized cryo-electron microscopy to reconstruct the structure of Bacteroides intestinalis virus ΦcrAss001. Reportedly, the analysis has revealed the structure of most of the virion proteins, including the identification of a novel protein fold named 'crass fold' in the muzzle protein. This fold is hypothesized to function as a gatekeeper, regulating the ejection of viral cargos. The study states that the ΦcrAss001 virus demonstrates a unique feature, possessing ample storage space within its capsid and tail for various virally encoded proteins, which is atypical for viruses of its kind.

According to the study, the findings from this study provide insights into the assembly and infection processes of crassviruses, which are highly abundant in the human gut. The study showcases how the ΦcrAss001 virus can house a significant amount of its DNA, along with numerous cargo proteins, within its structure. The discovery of a cargo protein present in both the capsid and the tail proposes a general mechanism for protein ejection, the study states, involving partial unfolding as they pass through the tail. The study says that this detailed structural analysis is a step towards understanding the complex mechanisms that underpin the functioning of these prevalent viruses within the human microbiome.

Springer Nature: Oliver Bayfield, Andrey Shkoporov, et al., Structural atlas of a human gut crassvirus, Nature (2023). https://doi.org/10.1038/s41586-023-06019-2