Significance Nearly all outer-membrane proteins (OMPs) in Gram-negative bacteria are inserted via the β -barrel assembly machinery (BAM) complex. Molecular dynamics simulations have revealed a persistent C-terminal strand kink of the core BAM component, BamA, which permits BamA to open laterally to the membrane. Experiments show that inhibiting kinking makes bacteria more susceptible to antibiotics. Kink-induced lateral gating may catalyze OMP insertion through a local disruption of the membrane, a pathway into the membrane, or both.