bioRxiv preprint doi: https://doi.org/10.1101/2021.02.17.431615; this version posted February 17, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-ND 4.0 International license. Gram-negative outer membrane proteins with multiple β-barrel domains Ron Solan1#, Joana Pereira2#, Andrei N. Lupas2*, Rachel Kolodny3*, Nir Ben-Tal1* 1 Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel. 2 Department of Protein Evolution, Max-Planck-Institute for Developmental Biology, Tübingen 72076, Germany. 3 Department of Computer Science, University of Haifa, Mount Carmel, Haifa, 3498838, Israel. # Co-first authorship *Correspondence: Andrei N. Lupas, Email:
[email protected]; Rachel Kolodny, Email:
[email protected]; Nir Ben-Tal, Web: http://bental.tau.ac.il, Email:
[email protected]; Abstract Outer membrane beta barrels (OMBBs) are found in the outer membrane of Gram-negative bacteria and eukaryotic organelles. OMBBs fold as antiparallel β-sheets that close onto themselves, forming pores that traverse the membrane. Currently known structures include only one barrel, of 8-36 strands, per chain. The lack of multi-OMBB chains is surprising, as most OMBBs form oligomers and some function only in this state. Using a combination of sensitive sequence-comparison methods and co-evolutionary analysis tools, we identify many proteins combining multiple beta barrels within a single chain; combinations that include 8-stranded barrels prevail.