  We identify three dimeric proteins whose mechanostability is anisotropic and
should exceed 1 nN along some directions. They come with distinct mechanical
clamps: shear-based, involving a cystine slipknot, and due to dragging of a
cystine plug through a cystine ring. The latter two mechanisms are topological
in nature and the cystine plug mechanism has not yet been discussed but it
turns out to provide the largest resistance to stretching. Its possible
applications in elastomers are discussed.
