Figure 6
Orientation preference for lutein. The frequency of observing docked lutein–StARD3LBD complexes is plotted as a function of steric clashes incurred for members of the `one portal' set with at least one potential hydrogen bond. Within the top 10% scoring group (fewer than 23 clashes; 836 of 8469 outcomes), the frequency for lutein molecules oriented with the ∊-ionone ring buried deep inside the cavity (yellow bars; n = 620) was 2.9-fold higher compared with the frequency for the opposite orientation with the β-ionone ring buried (blue bars; n = 216). This frequency difference meets the criteria for statistical significance with p < 0.00001 for a chi-squared test. Similarly strong frequency differences indicating that it is easier to place the ∊-ionone ring inside the tunnel-like cavity and the β-ionone ring outside portal 1 were observed if the analysis was repeated with Ω1 and Arg351 adopting their alternate conformations or with Ω1 deleted and Arg351 truncated to an alanine residue. |