Cas3

Cas3 is an ATP-dependent single-strand DNA (ssDNA) translocase/helicase enzyme that degrades DNA as part of CRISPR based immunity.

Cas3 is a "signature" protein of class 1 CRISPR systems and functions in a complex known as CASCADE, with other cas genes and a targeting RNA to degrade viral DNA.

In April 2019 Cornell University researcher Ailong Ke published a paper in the journal Molecular Cell describing a new gene editing CRISPR system, CRISPR-Cas3 which can efficiently delete long swaths of DNA from a targeted site in the human genome. This ability is superior to that achieved with the more common CRISPR-Cas9 systems.

CONAN, a CRISPR based diagnostic approach was developed utilising Cas3

Structure and function
Thermophile Thermobifida fusca Cas3 is a four domain protein with an N-terminal HD-type nuclease domain, followed by two RecA-like domains forming a superfamily 2 helicase motif, then the Cas3 specific linker and C-terminal domain. Single stranded DNA is passed 3′-to-5′ from the helicase domain to the nuclease domain where it is hydrolysed.