Omp_AT is a family of Gram-negative Gamma-proteobacteria outer membrane autotransporter beta-barrel proteins. Secondary structure prediction indicates a beta-barrel domain of 12 beta-strands. with an N terminal helix running along the central barrel axis perpendicular to the 12 antiparallel strands that form the barrel. Autotransporter translocation units defined by a beta-barrel of 12 to 14 antiparallel strands with an N terminal helix perpendicular to the barrel [1].

1: Protein domain of unknown function 3233 is a translocation domain of autotransporter secretory mechanism in gamma proteobacteria. Prakash A, Yogeeshwari S, Sircar S, Agrawal S; PLoS One. 2011;6:e25570. PMID:22073138