We and our partners use cookies and other tracking technologies to collect data relating to you to perform analytics, improve your experience of using our website, provide you with personalized ads and content based on your interactions with these and other websites and allow you to share content on social media. By clicking “Accept All Cookies”, you consent to this and to the sharing of this data with our partners. You can change your consent preferences at any time in the “Cookie Settings” section at the bottom of our website. Review our Cookie Notice to learn more about our practices.
Are there different CRISPR-associated system (Cas) proteins?
In bacterial and archaeal genomes, at least 45 distinct protein families have been identified to be associated with CRISPR loci.3 These CRISPR-associated system (Cas) proteins are used to classify CRISPR/Cas systems as Type I, II, or III. Type I systems are marked by the presence of cas3 (a single-stranded DNA nuclease and ATP-dependent helicase4), Type II by cas9 (a dual RNA-guided DNA endonuclease5), and Type III by cas10 (function unclear2). All CRISPR/Cas systems contain cas1 (a sequence specificity-free metal-dependent DNAse) and cas2 (a metal-dependent endoribonuclease). Both of these enzymes are involved in spacer acquisition.1
References:
1. K.S. Makarova, et al., “Unification of Cas protein families and a simple scenario for the origin and evolution of CRISPR-Cas systems,” Biol Direct 6:38, 2011.
2. D. Rath, et al., “The CRISPR-Cas immune system: biology, mechanisms and applications,” Biochimie 117:119-128, 2015.
3. D.H. Haft, et al., “A Guild of 45 CRISPR-Associated (Cas) Protein Families and Multiple CRISPR/Cas Subtypes Exist in Prokaryotic Genomes,” PLoS Comput Biol 1(6):e60, 2005.
4. T. Sinkunas, et al., “Cas3 is a single-stranded DNA nuclease and ATP-dependent helicase in the CRISPR/Cas immune system,” EMBO J 30(7):1335-1342, 2011.
5. M. Jinek, et al., “A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity,” Science 337(6096):816-821, 2012.
References:
1. K.S. Makarova, et al., “Unification of Cas protein families and a simple scenario for the origin and evolution of CRISPR-Cas systems,” Biol Direct 6:38, 2011.
2. D. Rath, et al., “The CRISPR-Cas immune system: biology, mechanisms and applications,” Biochimie 117:119-128, 2015.
3. D.H. Haft, et al., “A Guild of 45 CRISPR-Associated (Cas) Protein Families and Multiple CRISPR/Cas Subtypes Exist in Prokaryotic Genomes,” PLoS Comput Biol 1(6):e60, 2005.
4. T. Sinkunas, et al., “Cas3 is a single-stranded DNA nuclease and ATP-dependent helicase in the CRISPR/Cas immune system,” EMBO J 30(7):1335-1342, 2011.
5. M. Jinek, et al., “A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity,” Science 337(6096):816-821, 2012.
