| Abstract [eng] |
CRISPR-Cas is an antiviral system that provides adaptive immunity to prokaryotes. This system allows a cell to sample a fragment from invasive genetic material and incorporate it into its own genome. Adaptation is the core stage in providing immunity, when the sample is bound, processed and integrated into the CRISPR locus of the genome. Cas1 and Cas2 are proteins which are essential, but not neccessarily sufficient for integration. Often, additional proteins are required, such as Cas4, which performs a vast array of functions throughout the different types of systems. Recently, type V CRISPR-Cas systems have received increased interest due to the presence of small efector proteins – Cas9 analogs. Currently, little is known about these systems, especially adaptation. In this work, the V-F subtype CRISPR-Cas system was analyzed, which was discovered within metagenomic data, and posseses the adaptation proteins Cas1, Cas2 and Cas4 alongside the small effector protein Cas12f. It was unknown if Cas4 acted like its analogues found in other systems, or if it exhibited unique functions. Analysis of the adaptation complex structural models revealed that the V-F subtype Cas4 protein similarly to those found in some other Cas4-encoding CRISPR-Cas systems is responsible for PAM recognition during spacer acquisition, and forms a stable integration complex with Cas1 and Cas2 proteins. |
