Summary information and primary citation
- PDB-id
-
6xn4;
DSSR-derived features in text and
JSON formats
- Class
- RNA binding protein-RNA
- Method
- cryo-EM (3.35 Å)
- Summary
- Structure of the lactococcus lactis csm ctr_3:2
crispr-cas complex
- Reference
-
Sridhara S, Rai J, Whyms C, Goswami H, He H, Woodside W,
Terns MP, Li H (2022): "Structural
and biochemical characterization of in vivo assembled
Lactococcus lactis CRISPR-Csm complex." Commun
Biol, 5, 279. doi: 10.1038/s42003-022-03187-1.
- Abstract
- The small RNA-mediated immunity in bacteria depends on
foreign RNA-activated and self RNA-inhibited enzymatic
activities. The multi-subunit Type III-A CRISPR-Cas
effector complex (Csm) exemplifies this principle and is in
addition regulated by cellular metabolites such as divalent
metals and ATP. Recognition of the foreign or cognate
target RNA (CTR) triggers its single-stranded
deoxyribonuclease (DNase) and cyclic oligoadenylate (cOA)
synthesis activities. The same activities remain dormant in
the presence of the self or non-cognate target RNA (NTR)
that differs from CTR only in its 3'-protospacer flanking
sequence (3'-PFS). Here we employ electron cryomicroscopy
(cryoEM), functional assays, and comparative cross-linking
to study in vivo assembled mesophilic Lactococcus lactis
Csm (LlCsm) at the three functional states: apo, the CTR-
and the NTR-bound. Unlike previously studied Csm complexes,
we observed binding of 3'-PFS to Csm in absence of bound
ATP and analyzed the structures of the four RNA cleavage
sites. Interestingly, comparative crosslinking results
indicate a tightening of the Csm3-Csm4 interface as a
result of CTR but not NTR binding, reflecting a possible
role of protein dynamics change during activation.
