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Figure 3
(a) Cartoon representation of PpsRQ-PAS1. The PAS1 domain is coloured blue and the structured C-terminal part of the Q-linker helix is coloured red. Cys251 (pink) located in strand β51 (Fig. 2[link]) points towards a small cavity (shaped as a grey surface) that is frequently involved in cofactor binding of PAS domains. (b) Structure of a parallel PpsRQ-PAS1 dimer. The PpsRQ-PAS1 protomer is coloured according to (a), whereas the symmetry-related molecule (distinguished by a prime) is coloured in equivalent but lighter colours. The crystallographic twofold axis generating the dimer is shown in black. (c) Structure of the PpsRN-Q-PAS1 dimer. The N-domain of PpsRN-Q-PAS1 is coloured orange and its capping helix grey. The remaining structural elements are coloured according to (a). Protomer A is coloured in saturated colours and protomer B in light colours. Individual domains of different protomers are distinguished by superscript letters. (d) Structure of the PpsRΔHTH tetramer (PDB entry 4hh2 ; Winkler et al., 2013BB71) formed by two antiparallel dimers. Protomer C is coloured according to (c) and the additional PAS2 domain is shown in green. The dimer formed by protomers C and D (coloured purple) is shown as a cartoon representation, whereas that formed by protomers A (coloured light orange) and B (coloured grey) is depicted as a surface representation. (e) The octameric assembly of PpsRΔHTH represented by two tetramers generated by a crystallographic twofold axis (Winkler et al., 2013BB71). View along the twofold symmetry axis perpendicular to the plane (black symbol). One tetramer is shown as a cartoon representation and the second as a surface representation. Protomers A are coloured in light orange, B in grey, C in slate and D in dark purple, respectively. Individual domains of different protomers are distinguished by superscript letters and labels of the symmetry mate are marked with an additional prime. Note that the N-Q-PAS1 domains of protomers A and B exclusively stabilize the quaternary assembly.

Journal logoBIOLOGICAL
ISSN: 1399-0047
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