Team:Vilnius-Lithuania/Composite Part
Composite part
In this page we describe our favorite composite part which is I-F type Cascade complex of I-F type CRISPR-Cas system It can be found in Parts Registry - BBa_K1773022.
Cascade with pLux/cI right promoter and strong RBS
I-F type Cascade complex of I-F type CRISPR-Cas system. The Cascade complex distinguishes target DNA and recruits Cas3 (BBa_K1773003) protein, which degrades the target DNA. Cascade complex is comprised of four proteins: Csy1, Csy2, Csy3 and Cas6f. crRNA region coding crRNAs is necessary for complete Cascade complex.
Usage and Biology
Cascade (CRISPR Associated Complex for Antiviral Defence) complex is an essential component of I-type CRISPR-Cas systems, because it distinguishes foreign DNA and promotes its degradation. This ribonucleoprotein complex is coded by operon of 4 genes: Csy1, Csy2, Csy3 and Cas6f, with stoichiometry of 1:1:6:1 respectively. Also it has a crRNA molecule, which acts like a guide, that brings the whole complex to the target dsDNA sequence. Each Cascade complex has a unique Protospacer Adjacent Motive (PAM) recognition site. The recognizable PAM sequence of this specific I-F Cascade complex from Aggregatibacter actinomycetemcomitans recognizes CC nucleotides directly upstream of the protospacer (the target sequence). In other words, a target sequence needs to have a CC pair on the non-complementary strand of DNA -2 -1 positions of the protospacer. When Cascade complex finds and recognizes the DNA target, then Cas3 (BBa_K1773003) is recruited for DNA degradation.