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CRISPR and crRNAs

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Bacteria and archaea are susceptible to viral infections just like eukaryotes; therefore, they have developed a unique adaptive immune system to protect themselves. Clustered regularly interspaced short palindromic repeats and CRISPR-associated proteins (CRISPR-Cas) are present in more than 45% of known bacteria and 90% of known archaea.
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Related Experiment Video

Updated: Feb 6, 2026

Substrate Generation for Endonucleases of CRISPR/Cas Systems

Substrate Generation for Endonucleases of CRISPR/Cas Systems

Published on: September 8, 2012

PAM identification by CRISPR-Cas effector complexes: diversified mechanisms and structures.

Daniel Gleditzsch¹, Patrick Pausch², Hanna Müller-Esparza¹

¹a Prokaryotic Small RNA Biology Group, Max-Planck-Institute for terrestrial Microbiology & LOEWE Center for synthetic Microbiology (Synmikro) , Marburg , Germany.

|August 16, 2018

Summary

Prokaryotic CRISPR-Cas systems use Cas proteins to target foreign DNA. This review details diverse PAM recognition strategies and structures, crucial for specificity and defense against viral evasion.

Keywords:

CRISPR Cas proteins DNA recognition PAM ribonucleoproteins

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Substrate Generation for Endonucleases of CRISPR/Cas Systems

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Gene Digital Circuits Based on CRISPR-Cas Systems and Anti-CRISPR Proteins

Gene Digital Circuits Based on CRISPR-Cas Systems and Anti-CRISPR Proteins

Published on: October 18, 2022

Area of Science:

Microbiology
Molecular Biology
Genetics

Background:

CRISPR-Cas systems provide adaptive immunity in prokaryotes.
Cas proteins identify and destroy foreign genetic material using specific targeting mechanisms.
Protospacer Adjacent Motifs (PAMs) are critical for distinguishing self from non-self DNA.

Purpose of the Study:

To review known Protospacer Adjacent Motif (PAM) recognition strategies across all CRISPR-Cas types.
To highlight the diversity of Cas protein effector complexes and their domain architectures.
To explain how these mechanisms ensure target specificity and overcome viral anti-CRISPR strategies.

Main Methods:

Literature review of CRISPR-Cas systems and PAM recognition.
Analysis of available structural data for Cas protein effector complexes.
Comparative analysis of PAM-interacting domains and their evolutionary adaptations.

Main Results:

CRISPR-Cas systems exhibit a wide array of PAM recognition strategies.
Cas proteins utilize diverse domain architectures to interact with PAM sequences.
Structural data reveals intricate mechanisms for ensuring target specificity.

Conclusions:

PAM recognition is a key determinant of CRISPR-Cas system specificity and efficacy.
The evolution of PAM-interacting domains allows adaptation to viral defense mechanisms.
Understanding these strategies is vital for harnessing CRISPR-Cas technology.