bc9b00703_si_001.pdf (470.99 kB)
Discovery and Evaluation of Peptide Ligands for Selective Adsorption and Release of Cas9 Nuclease on Solid Substrates
journal contribution
posted on 2019-12-08, 20:13 authored by Kevin Day, Raphael Prodromou, Sahand Saberi Bosari, Ashton Lavoie, Mohammad Omary, Connor Market, Adriana San Miguel, Stefano MenegattiThe rapid expansion of CRISPR in biotechnology, medicine,
and bioprocessing
poses an urgent need for advanced manufacturing of Cas nucleases.
The lack of Cas-targeting ligands, however, prevents the development
of platform processes for purifying this class of molecules. This
work represents the first effort at developing short synthetic Cas9-binding
peptides and demonstrates their applicability as affinity ligands
for the purification of a Cas nuclease. Candidate Cas9-targeting peptides
were initially identified by screening a solid-phase peptide library
against a model mixture of Streptococcus pyogenes Cas9 spiked in Escherichia coli cell lysate. An
ensemble of homologous sequences was identified, conjugated on Toyopearl
resin, and evaluated by Cas9 binding studies to identify sequences
providing selective Cas9 capture and efficient release. In
silico docking studies were also performed to evaluate the
binding energy and site of the various peptides on Cas9. Notably,
sequences GYYRYSEY and YYHRHGLQ were shown
to target the RecII domain of Cas9, which is not involved in nuclease
activity and was targeted as an ideal binding site. The peptide ligands
were validated by purifying Cas9 from the E. coli lysate in dynamic conditions and through measurements of binding
capacity and strength (Qmax and KD). The resulting values of Qmax = 4–5 mg Cas9 per mL of resin and KD ∼ 0.1–0.3 μM, product recovery (86–89%),
and purity (91%–93%) indicate that both peptides, and YYHRHGLQ
in particular, can serve as capture ligands in a platform purification
process of Cas9.