Difference between revisions of "Part:BBa K3853011"

Revision as of 22:35, 15 October 2021

dCas9-SpyCatcher

This part consists of defective endonuclease dCas9(BBa_K3853003), modified immunoglobulin-like domain SpyCatcher and Ser/Gly linker(S/G linker). S/G linker is applied to link dCas9 with SpyCatcher. dCas9 can specifically target and bind dsDNA under the mediation of single-guide RNA (sgRNA), meanwhile, SpyCatcher is usually used for protein ligation. dCas9-SpyCatcher has been reported as connection system to assemble protein-nucleic-acid complex. We use BBa_K3853055 to construct the expression system and to express and to purify the protein.

Biology

The dCas9 gene use in this experiment was derived from two nuclease cleavage active domains of Streptococcus pyogenes Cas9 gene, RuvC and HNH, and simultaneously inactivate by artificial single point mutation (D10A & H840A). dCas9 can recognize with single-guide RNA (sgRNA), and combine with it to form a complex but does not play a cutting role. Through complementary base pairing between sgRNA and artificially design dsDNA, multiple dCas9 can be indirectly connect to dsDNA to form a complex. The SpyCatcher/SpyTag system is a bio-coupling technology connect by isopeptide bonds, which is derive from the modification of immunoglobulin like collagen adhesin domain (CnaB2)^[1]. In the CnaB2 domain, Glu77 catalyzes the nucleophilic attack on the carbonyl carbon of Asp117 by unprotonic amines in nearby Lys31, resulting in the spontaneous formation of intramolecular isopeptide bonds. Based on the principle of isopeptide bond formation, CnaB2 is split into two parts that could be recombined and covalently reacted: a peptide containing active Asp representing the c-terminal β chain and a protein partner from the rest of the protein. After modification, the peptide SpyTag is formed with 13 amino acids (AHIVMVDAYKPTK) and the protein Spycatcher with 138 amino acids (15kDa). The two can spontaneously form isopeptide bond and bond stably^[2]. This part is the fusion of dCas9 and SpyCatcher.

Usage

Characterization

References

[1] Zakeri, B. et al. Peptide tag forming a rapid covalent bond to a protein, through engineering a bacterial adhesin. Proc Natl Acad Sci U S A 109, E690-697, doi:10.1073/pnas.1115485109 (2012).

[2] Reddington, S. C. & Howarth, M. Secrets of a covalent interaction for biomaterials and biotechnology: SpyTag and SpyCatcher. Current opinion in chemical biology 29, 94-99, doi:10.1016/j.cbpa.2015.10.002 (2015).

Sequence and Features