The beta-link is a composite protein motif consisting of a G1beta beta-bulge and a type II beta-turn, and is generally found at the end of two adjacent strands of antiparallel beta-sheet. The 1,2-positions of the beta-bulge are also the 3,4-positions of the beta-turn, with the result that the N-terminal portion of the polypeptide chain is orientated at right angles to the beta-sheet. Here, it is reported that the beta-link is frequently found in certain protein folds of the SCOPe structural classification at specific locations where it connects a beta-sheet to another area of a protein. It is found at locations where it connects one beta-sheet to another in the beta-sandwich and related structures, and in small (four-, five- or six-stranded) beta-barrels, where it connects two beta-strands through the polypeptide chain that crosses an open end of the barrel. It is not found in larger (eight-stranded or more) beta-barrels that are straightforward beta-meanders. In some cases it initiates a connection between a single beta-sheet and an alpha-helix. The beta-link also provides a framework for catalysis in serine proteases, where the catalytic serine is part of a conserved beta-link, and in cysteine proteases, including M(pro) of human SARS-CoV-2, in which two residues of the active site are located in a conserved beta-link.