@article{171021,
  author = {Elizabeth M. Hart and Meera Gupta and Martin W{\"u}hr and Thomas J. Silhavy},
  title = {The gain-of-function allele bamAE470K bypasses the essential requirement for BamD in β-barrel outer membrane protein assembly},
  abstract = { The assembly of β-barrel outer membrane proteins (OMPs) is broadly conserved in diderm bacteria as well as in mitochondria and chloroplasts. The β-barrel assembly machine (BAM), which assembles OMPs into the outer membrane of gram-negative microbes, contains two essential proteins, BamA and BamD. Here we identify a genetic background in which BamD is nonessential, indicating that BamD does not function in OMP catalysis, but rather plays a regulatory role in OMP assembly. BamD is not conserved in the complexes that assemble OMPs in chloroplasts and mitochondria, likely because these organelles, unlike bacteria, inhabit a carefully controlled cytoplasmic environment.The outer membrane (OM) of gram-negative bacteria confers innate resistance to toxins and antibiotics. Integral β-barrel outer membrane proteins (OMPs) function to establish and maintain the selective permeability of the OM. OMPs are assembled into the OM by the β-barrel assembly machine (BAM), which is composed of one OMP{\textemdash}BamA{\textemdash}and four lipoproteins{\textemdash}BamB, C, D, and E. BamB, C, and E can be removed individually with only minor effects on barrier function; however, depletion of either BamA or BamD causes a global defect in OMP assembly and results in cell death. We have identified a gain-of-function mutation, bamAE470K, that bypasses the requirement for BamD. Although bamD::kan bamAE470K cells exhibit growth and OM barrier defects, they assemble OMPs with surprising robustness. Our results demonstrate that BamD does not play a catalytic role in OMP assembly, but rather functions to regulate the activity of BamA. },
  year = {2020},
  journal = {Proceedings of the National Academy of Sciences},
  publisher = {National Academy of Sciences},
  issn = {0027-8424},
  url = {https://www.pnas.org/content/early/2020/07/15/2007696117},
  doi = {10.1073/pnas.2007696117},
  language = {eng},
}