Biochemical and biophysical research communicationsFeb 22, 2026

How AcrIIA26 blocks the CRISPR-SpyCas9 gene-editing system

CRISPR Gene Editing Weekly Brief ↗PubMed ↗DOI ↗

Updated Feb 23, 2026

Abstract

The cryo-EM structure of the SpyCas9-sgRNA-AcrIIA26 complex shows a two-domain architecture.

AcrIIA26 consists of two domains: a 5A domain that binds to the PI and WED domains of Cas9, and a 4A domain that interacts with the REC2 domain.
This dual interaction blocks the binding of target DNA and prevents necessary conformational changes for cleavage.
AcrIIA26 can bind to Cas9 independently of sgRNA, allowing for modulation of gene editing over an extended time frame.
The findings provide insight into the molecular mechanism of AcrIIA26 and suggest new strategies for regulating SpyCas9.

Simplified

In the ongoing arms race between bacteria and phages, CRISPR-Cas systems and anti-CRISPR proteins (Acrs) have evolved to counteract one another. Recently, AcrIIA26 from Streptococcus sp. was identified as a modulator of SpyCas9 activity, although its molecular mechanism remains unclear. Here, we present the cryo-EM structure of the SpyCas9-sgRNA-AcrIIA26 complex, revealing a two-domain architecture. The 5A domain of AcrIIA26 binds the PI and WED domains of Cas9, while the 4A domain contacts the REC2 domain. This dual interaction sterically blocks target DNA binding and prevents the conformational changes required for cleavage. Notably, AcrIIA26's sgRNA-independent binding to Cas9 allows the modulation of gene editing across an extended temporal window. Our study elucidates the molecular mechanism of AcrIIA26 and provides novel strategies for precise SpyCas9 regulation.

Full Text

Full text is available at the source.

View Full Text ↗

Funding

Competing interests

Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

PubMed

How AcrIIA26 blocks the CRISPR-SpyCas9 gene-editing system

Abstract

Full Text

Funding

Competing interests

You found one interesting study. We’ll send the next 7.

What Lands in Your Inbox Each Week:

Recent issues from the crispr gene editing brief