Fig. 5: Porin localization determines the formation of helical PapS ribbons.
a Scheme showing the locations of the periplasmic loops (vertical grey lines) in the Por39 and Por41 polypeptides and the amino acid conservation of periplasmic loop 2, determined by aligning the sequences of all Por39/41 homologs identified in the nr database (NCBI) by BLAST analysis. The aspartate residue mutated in this study is highlighted in red. b Morphology of R. rubrum cells carrying the por39D71S (SP215) or por41D71S (SP150) alleles in place of the respective wild-type genes, imaged by phase-contrast microscopy. Bar: 5 µm. c Superplots showing the distribution of cell sinuosities in populations of R. rubrum wild-type (S1), por39D71S (SP215) and por41D71S (SP150) cells. The data are presented as described for Fig. 1f (n = 100 cells per replicate). The statistical significance (p value) of differences between the wild type and the two mutant strains is indicated (unpaired two-sided Welch’s t-test). d Colocalization of PapS-mNG and mCh-Por39 in the por41D71S background. Cells (SP131) were cultivated in the absence (untreated) or presence (+) of cefalexin prior to imaging. The images show representative cells analyzed by widefield epifluorescence microscopy (untreated) and 3D-SIM (+ Cefalexin) (n = 3 biological replicates). Bar: 5 µm. The area overlap of the PapS-mNG and mCh-Por39 signals in the 3D-SIM images is 82.5% (see also Supplementary Data 4). e Bubble plot showing the apparent single-molecule diffusion rates of PapS-PAmCh in the wild-type (SP04) and por41D71S (SP183) backgrounds. The data for PapS-PAmCh in the wild-type background are replotted from Fig. 3f as a reference. The diffusive and immobile populations have mean apparent diffusion coefficients of 0.0657 µm2 s-1 and 0.0191 µm2 s-1, respectively. The number of cells analyzed is given in Supplementary Data 3. Source data are provided as a Source Data file.
