| Type: | Family | Name: | CRISPR-associated protein Cas4, PREFRAN subtype |
| Description: | Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) are a family of DNA direct repeats separated by regularly sized non-repetitive spacer sequences that are found in most bacterial and archaeal genomes []. CRISPRs appear to provide acquired resistance against mobile genetic elements (viruses, transposable elements and conjugative plasmids. CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). In addition, there are many protein families known as CRISPR-associated sequences (Cas), which are encoded in the vicinity of CRISPR loci []. CRISPR/cas gene regions can be quite large, with up to 20 different, tandem-arranged cas genes next to a CRISPR cluster or filling the region between two repeat clusters. Cas genes and CRISPRs are found on mobile genetic elements such as plasmids, and have undergone extensive horizontal transfer. Cas proteins are thought to be involved in the propagation and functioning of CRISPRs. Some Cas proteins show similarity to helicases and repair proteins, although the functions of most are unknown. Cas families can be divided into subtypes according to operon organisation and phylogeny. Members of this family are the Cas4 protein of a novel CRISPR subtype, PREFRAN, found in Prevotella bryantii B14, Prevotella disiens FB035-09AN, Francisella tularensis subsp. novicida, Francisella philomiragia, Butyrivibrio proteoclasticus B316, Helcococcus kunzii ATCC 51366, etc. | Short Name: | Cas4_PREFRAN |
