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. 2011 Dec 9;50(50):11942-6.
doi: 10.1002/anie.201105648. Epub 2011 Oct 27.

Solution NMR Structure of Proteorhodopsin

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Free PMC article

Solution NMR Structure of Proteorhodopsin

Sina Reckel et al. Angew Chem Int Ed Engl. .
Free PMC article

Figures

Figure 1
Figure 1
Structure of PR. a) Bundle of the 20 conformers with lowest CYANA target function obtained from structure calculation. Helices are color-coded from helix A in dark blue to helix G in red. b) Cartoon representation of the conformer with the lowest CYANA target function seen from the side and from the top. In the lower panel helices are additionally labeled A-G.
Figure 2
Figure 2
Assignment and field-dependent line broadening of PR. a) 96% of the backbone resonances of PR were assigned (grey color). Residues that could not be assigned are depicted in red spheres (Y76, M77, C107) and those with partial backbone assignments in blue spheres. b) The field-dependent line broadening is illustrated for three representative resonances. [15N,1H]-TROSY spectra of selectively 15N-MRY-labeled PR were measured at different Bo field strengths as indicated in each spectrum. While most resonances remain unaffected by the field strength, resonances of R80, M79 and R94 disappear almost completely at 950 MHz.
Figure 3
Figure 3
Distance information for the structure calculation of PR. a) Representative plane of the 4D [13C,13C]-separated NOESY recorded with non-uniform sampling. b) Altogether 137 medium- to long-range NOEs were obtained for methyl groups and Trp side chains of an AILMTVW-labeled sample connecting the individual transmembrane helices.
Figure 4
Figure 4
Schiff base environment in PR. a) [13C,1H]-SOFAST-HMQC of 15N,13C-His-labeled PR. Only one additional His residue in Strep-tagged PR enables the assignment of H75 at pH 5. The spectrum shows the low signal-to-noise ratio of the imidazole-ring resonances of H75. Natural abundance background signals are labeled by the red asterisk. b) Close up of the retinal binding pocket with retinal shown in gray sticks, the Schiff base nitrogen highlighted in blue and residues that were included into the modeling colored by element.
Figure 5
Figure 5
B-C loop of PR and its three homologues bacteriorhodopsin (BR), sensory rhodopsin II (SRII) and xanthorhodopsin (XR) (PDB ID: 1C3W, 2KSY and 3DDL respectively). In PR an anti-parallel β-sheet between helices B and C as observed in the other three structures is not present. Sequence alignment further supports these findings as PR possesses a significantly shortened sequence in this region which favors the formation of a β-turn rather than two extended β-strands (Supporting Information Figure S8).

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