Interaction Surface of Bacteriophage P4 Protein Psu Required for Complex Formation with the Transcription Terminator Rho

The First Structure of Polarity Suppression Protein, Psu from Enterobacteria Phage P4, Reveals a Novel Fold and a Knotted Dimer

“…Multiple sequence alignment of Psu-like proteins, found in strains of different species as part of cryptic prophages in their genome (6), reveals that residues involved in the packing of coiled-coil (a and d positions) are highly conserved (Fig. 3).…”

“…Extensive mutational and crosslinking studies suggests that the interaction of Psu with Rho is direct and specific, mediated by the C-terminal tail of Psu, whereas the N-terminal domain of Psu maintains the conformational integrity of the C-terminal tail (6). However, the atomic structure of Psu, its domain organization and assembly remains unknown.…”

A NusG paralogue from Mycobacterium tuberculosis, Rv0639, has evolved to interact with ribosomal protein S10 (Rv0700) but not to function as a transcription elongation–termination factor

“…S10 proteins were Histagged at the N-terminus. Transformants were inoculated in 50 ml LB and were grown at 37 uC until the OD 600 reached y0.4 were then induced with 0.1 mM IPTG for protein expression, and the induction was continued for 3 h. The rest of the procedures for the pull-down assay were performed by following published methods (Pani et al, 2009).…”

“…The T7A1-lt R1 template was PCR amplified from the plasmid pRS604 (Pani et al, 2009) using primers RS58 and RS333. Reactions were performed in Ec RNAP transcription buffer [25 mM Tris/HCl (pH 8.0), 5 mM MgCl 2 , 50 mM KCl, 1 mM DTT and 0.1 mg BSA ml 21 ] at 37 uC.…”

RNA remodeling by hexameric RNA helicases

“…Salient illustrations of these features are provided by the bacterial, ring-shaped RNA chaperone Hfq which binds U-rich and A-rich substrates on, respectively, its proximal and distal faces 43 and by toroidal AAA + -enhancer binding proteins which recognize σ 54 -dependent promoter elements and the σ 54 -RNAP holoenzyme from opposite faces as well. 44 Rho may thus have evolved as a ring-shaped factor because this configuration optimizes its intricate and dynamic interaction network with the RNA transcript, the RNAP, NusG and other important factors (or inhibitors) 45,46 during transcription. 47,48 The P4 packaging motors of Pseudomonas phages, however, are pore-like structures by functional necessity and therefore adopt the classical ring-shaped architecture of other viral portals to package RNA genomes into the phage procapsids.…”