Figure 4. Some structural details.

(A) Two HPII molecules and their interaction partners, two Hfq hexamers. Hfq subunits are color-coded as in Figs. 3B and 4B, and HPII is displayed in tan (the C-terminal lobe) and in violet (the other parts) with heme in blue. “P” and “D” denote the proximal and distal sides of the Hfq hexamer, respectively. (B) Hfq hexamer viewed from the distal side. Residues for binding to HPII are drawn in space-filling representation (see also Table S2 in File S1) with the single-letter amino acid code for Tyr 25 and Asn 28 in subunit 5 (see Fig. 5). Atoms are color-coded as: carbon, yellow; nitrogen, blue; and oxygen, red. “α1” denotes the N-terminal α-helix and “β1” – “β5” β-strands. Numbers 1 - 6 in A and B indicate the subunit number in the Hfq hexamer. Only the Hfq subunits on the front side have the number in A for clarity.