PAM
Pronunciation: pam
Also written as: PAM — Protospacer Adjacent Motif
A short DNA sequence immediately flanking the target site that is required for Cas nuclease recognition and cleavage. Always rendered in full capitals.
Full Definition
The protospacer adjacent motif (PAM) is a 2–6 nucleotide sequence located immediately 3′ or 5′ of the gRNA target sequence on the non-template strand. It is essential for Cas9 (NGG for SpCas9) and other Cas variants to bind and cleave DNA. Editors should always render it as 'PAM' in capitals. In detailed methods sections, the specific PAM sequence may be written in single-letter nucleotide code (e.g., NGG, NNGRRT). PAM is not to be confused with the protospacer sequence itself, which is the target region complementary to the gRNA.
Usage
Usage note: Always capitalised as 'PAM'. Nucleotide codes within PAM sequences (e.g., NGG) are written in capitals with no spaces.
In Context
- "The SpCas9 nuclease requires an NGG PAM sequence immediately downstream of the target site." — Methods section
- "PAM-relaxed variants of Cas9 have expanded the targetable genome space." — Review article