Cryo-EM structures of Escherichia coli Ec86 retron complexes reveal architecture and defence mechanism.
Nat Microbiol
; 7(9): 1480-1489, 2022 09.
Article
em En
| MEDLINE
| ID: mdl-35982312
ABSTRACT
First discovered in the 1980s, retrons are bacterial genetic elements consisting of a reverse transcriptase and a non-coding RNA (ncRNA). Retrons mediate antiphage defence in bacteria but their structure and defence mechanisms are unknown. Here, we investigate the Escherichia coli Ec86 retron and use cryo-electron microscopy to determine the structures of the Ec86 (3.1 Å) and cognate effector-bound Ec86 (2.5 Å) complexes. The Ec86 reverse transcriptase exhibits a characteristic right-hand-like fold consisting of finger, palm and thumb subdomains. Ec86 reverse transcriptase reverse-transcribes part of the ncRNA into satellite, multicopy single-stranded DNA (msDNA, a DNA-RNA hybrid) that we show wraps around the reverse transcriptase electropositive surface. In msDNA, both inverted repeats are present and the 3' sides of the DNA/RNA chains are close to the reverse transcriptase active site. The Ec86 effector adopts a two-lobe fold and directly binds reverse transcriptase and msDNA. These findings offer insights into the structure-function relationship of the retron-effector unit and provide a structural basis for the optimization of retron-based genome editing systems.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
DNA Polimerase Dirigida por RNA
/
Escherichia coli
Idioma:
En
Ano de publicação:
2022
Tipo de documento:
Article