Unfolding the bridge between transcription and translation

Abstract

Transcription antiterminator RfaH alternates between closed (inactive) and open (activated) conformation. In this issue of Cell, Burmann et al. show that opening is accompanied by dramatic all-α to all-β refolding of its C-terminal domain. Each of the folds has a distinct function: all-α-fold acts as a specificity determinant, directing RfaH to a small subset of operons, whereas the all-β-fold recruits ribosome, thereby coupling RfaH-stimulated transcription to translation.

Figure 1. Conformational Switch that Really Matters

(A) Closed and open conformations of E. coli RfaH. (Left) Closed conformation (2oug,a; Belogurov et al., 2007). N-terminal (yellow) and C-terminal (blue) domains are mesh and cartoon. (Right) Homology model (adding 2lcl as a template) of the open conformation (Burmann et al., 2012). N- and C-terminal domains are mesh and cartoon. (B) Part of the DNA-binding patch of the RfaH N-terminal domain is obscured by interactions with C-terminal domain in the closed conformation. E. coli RfaH (2oug,a) N- and C-terminal domains are mesh and cartoon; DNA-binding patch residues are red sticks (Tyr8, Cys9, Lys10, Gly12, Arg16, Pro52, Asn53, Thr72, and Val75) or red spheres (Leu6, Tyr54, and Val79). The last three are packed against C-terminal domain residues Leu143 and Ile146 (blue spheres).