Abstract
Many proteins of viruses infecting hyperthermophilic Crenarchaeota have no detectable homologs in current databases, hampering our understanding of viral evolution. We used sensitive database search methods and structural modeling to show that a nucleocapsid protein (TP1) of Thermoproteus tenax virus 1 (TTV1) is a derivative of the Cas4 nuclease, a component of the CRISPR-Cas adaptive immunity system that is encoded also by several archaeal viruses. In TTV1, the Cas4 gene was split into two, with the N-terminal portion becoming TP1, and lost some of the catalytic amino acid residues, apparently resulting in the inactivation of the nuclease. To our knowledge, this is the first described case of exaptation of an enzyme for a virus capsid protein function.ReviewersThis article was reviewed by Vivek Anantharaman, Christine Orengo and Mircea Podar. For complete reviews, see the Reviewers’ reports section.Electronic supplementary materialThe online version of this article (doi:10.1186/s13062-015-0093-2) contains supplementary material, which is available to authorized users.
Highlights
Many proteins of viruses infecting hyperthermophilic Crenarchaeota have no detectable homologs in current databases, hampering our understanding of viral evolution
Concluding remarks Cas4 nuclease is a conserved component of the CRISPRCas systems
It appears likely that the ancestor of Thermoproteus tenax virus 1 (TTV1) encoded a functional Cas4 nuclease which could participate in certain aspects of genome replication or repair
Summary
Many proteins of viruses infecting hyperthermophilic Crenarchaeota have no detectable homologs in current databases, hampering our understanding of viral evolution. We used sensitive database search methods and structural modeling to show that a nucleocapsid protein (TP1) of Thermoproteus tenax virus 1 (TTV1) is a derivative of the Cas nuclease, a component of the CRISPR-Cas adaptive immunity system that is encoded by several archaeal viruses. In TTV1, the Cas gene was split into two, with the N-terminal portion becoming TP1, and lost some of the catalytic amino acid residues, apparently resulting in the inactivation of the nuclease. To our knowledge, this is the first described case of exaptation of an enzyme for a virus capsid protein function.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have