Figure 2.

Posterior probability plots and predicted transmembrane segments for the multidrug efflux transporter AcrB, a protein with known 3-dimensional structure (PDB code: 1IWG). In the upper graph we can see the unconstrained prediction. The red bars indicate the predicted transmembrane segments whereas the black bars, the observed segments. There are two missed transmembrane helices and a falsely predicted one. In the lower part, we can see the constrained prediction, after incorporating the experimental information derived from cysteine-scanning mutagenesis experiments [46]. Green arrows indicate the experimentally verified localisation of a residue in the cytoplasm, whereas blue ones indicate the experimentally verified localisation to the extracellular (periplasmic) space. We observe a remarkable agreement of the constrained prediction with the known structure.