Cross-section of the protein molecules and tunnel profiles of DmmA, DhlA, and LinB. (A to C) Cross-sections at main access tunnels of DmmA (A), DhlA (B), and LinB (C) with displayed protein surface. (D) Diameter of the main access tunnels calculated by CAVER for DmmA (solid line), DhlA (dotted line), and LinB (dashed line). No bottleneck is observed for DmmA, as the diameter is increasing toward the tunnel entrance. DhlA and LinB have bottlenecks at distances of 6.5 and 9.8 Å from the active site, respectively.