Fig. 1: Phage defence and structures of a type I-A retron.
From: Structural basis of antiphage defence by an ATPase-associated reverse transcriptase
a Schematic of the type I-A retron operon. The retron encodes an RT, ncRNA, ATPase and HNH nuclease. Both the ATPase and HNH nuclease feature C-terminal extensions. b Phage challenge assay demonstrate that the type I-A retron from E. coli protects against phages T3 and T5. The empty vector (EV) control exhibits no defence. Data shown is representative of n = 2 replicates. c A covariance model for ncRNA from type I-A retrons generated from 70 sequences. d Size exclusion chromatography (SEC) of the affinity-purified type I-A retron reveals a monodispersed peak with an estimated molecular weight of 350 kDa. The chromatogram is representative of n = 3 biological replicates. e SDS-PAGE analysis of the main SEC peak reveals proteins corresponding to the ATPase, RT, and HNH. Nucleic acids (ncRNA and msDNA) associated with the retron complex treated with either DNase or RNase and resolved using a 14% urea-PAGE. Data is representative of n = 3 biological replicates. f Reconstructed density maps of the type I-A retron. HNH is bound asymmetrically in an up or down orientation to one of the ATPase homodimers.
