Bètabarrelstructuren

Bètabarrelstructuren, or beta-barrel structures, are protein folds in which beta-strands are arranged in a cylindrical, barrel-shaped topology. The strands are connected by short loops and form a continuous exterior surface and, in many cases, an interior pore. The most prominent beta-barrels are transmembrane proteins located in the outer membranes of Gram-negative bacteria, mitochondria, and chloroplasts, where they often function as porins or transport channels. A typical beta-barrel contains roughly eight to twenty-two beta-strands, arranged antiparallel to each other, though variations occur.

Structural features include a pore diameter determined by the barrel’s length and strand count, and loop regions that influence selectivity and gating. The outward-facing side of the barrel is commonly hydrophobic, stabilizing insertion in the membrane, while polar residues line the interior to interact with transported solutes. The arrangement of strands and turns gives rise to a stable, curved surface that can accommodate a range of substrates.

Formation and biogenesis involve synthesis in the cytosol, targeted translocation across membranes, and assisted folding by chaperones and assembly machineries (for example, the BAM complex in bacteria). In mitochondria and chloroplasts, organelle-specific translocases support proper integration and folding.

Functions encompass channeling and selective transport of nutrients and metabolites, waste removal, and roles as structural scaffolds or enzyme complexes. Because of their membrane localization and central role in permeability, beta-barrel structures are of interest in antibiotic targeting, protein design, and nanotechnology.

Research methods include X-ray crystallography, cryo-electron microscopy, and NMR, along with computational topology and sequence-based predictions to infer strand number and arrangement.