PH-dependent dimerization and salt-dependent stabilization of the N-terminal domain of spider dragline silk - Implications for fiber formation

One of the toughest protein fibers: The N-terminal domain (NTD) of spider dragline silk shows a pH-dependent monomer-dimer equilibrium: The N-terminal domain silk protein is stored as a stabilized monomer at neutral pH and high salt concentration, whereas during fiber assembly at a lower pH value this domain is able to form antiparallel dimers. Multivalent linking results in endless and highly stable fibers (see picture).