EC Number   |
General Information |
Reference |
|---|
   3.1.12.1 | evolution |
a capsid protein, TTV1 nucleocapsid protein TP1, of a filamentous archaeal virus, Thermoproteus tenax virus 1 (TTV1), evolved relatively recently through exaptation from a CRISPR-associated Cas4 nuclease. The corresponding surface in Cas4 is shielded by the C-terminal domain, suggesting that removal of this domain is a prerequisite for the transformation of the ancestral TTV1 Cas4 into a nucleocapsid protein |
749996 |
| 3.1.12.1 | evolution |
Cas4 proteins exhibit low sequence similarity among themselves and are currently classified into 2 main classes: DUF83 and DUF911. The genome of Sulfolobus solfataricus encodes five Cas4 like protein comprising low sequence similarity (below 30%). Out of them, SSO0001, SSO1392, and SSO1449 belong to DUF83 class, and SSO1391 and SSO1451 belong to DUF911 class. SSO1391 has been reported to show broad range cleavage specificity for cleaving ssDNA in both the directions (5'-3') and (3'-5') (DUF911). By contrast, members of DUF83 class cleave the ssDNA substrate only in the direction 5'-3'. The overall three-dimensional structural fold of DUF83Ss and DUF83Pc appears to be conserved. The separation of Cas4 proteins of DUF83 class into 2 separate branches hints at the possibility of specific sites which guide the evolutionary divergence between Cas4 proteins of the 2 clades, prediction of discriminative motifs among the two subclasses of DUF83 Cas4 proteins through motif analysis, overview. Divergence type I analyses of two clusters and their intra molecular hydrogen bonding with other residues |
-, 751365 |
| 3.1.12.1 | evolution |
the Pyrococcus furiosus genome harbors two distinct cas4 genes, one in a cas4-1/ cas1/cas2 operon and the other cas4-2 at a remote location not associated with CRISPR |
751557 |
| 3.1.12.1 | malfunction |
in TTV1, the Cas4 gene has been 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 |
749996 |
| 3.1.12.1 | malfunction |
while cas4-2 deletion does not increase adaptation frequency overall, it dramatically increases incorporation of the duplexed DNA oligonucleotide. The plasmid-expressed wild-type Cas4-2 rescues spacer sizes and the downstream NW motif, but the nuclease-defective Cas4-2 does not |
751558 |
| 3.1.12.1 | more |
analysis of protospace adjacent motif (PAM) sequence recognition by the Cas4 isozymes, overview |
751558 |
| 3.1.12.1 | more |
Cas4 forms a tight complex with Cas1 in vitro, compatible with the fact that the cas4 gene is usually encoded next to or in fusion with cas1 |
751557 |
| 3.1.12.1 | more |
catalytic mechanism analysis |
751557 |
| 3.1.12.1 | more |
three-dimensional structure modelling |
749996 |
| 3.1.12.1 | physiological function |
a potential functional role of the enzyme and other Cas4 proteins in CRISPR (Clusters of Regularly interspaced Palindromic Repeats) immunity is based on the presence of 5' to 3' exonuclease and DNA unwinding activities, which produce 3'-ssDNA overhangs as potential intermediates in the process of new spacer addition. The toroidal structures of the enzyme can serve as sliding clamps for other Cas proteins |
-, 725211 |
