Exceptional mechanical stability of the spider silk C-terminal domain

The helical C-terminal domain (CTD) of spider silk proteins exhibits exceptionally high mechanical stability, with an unfolding force of ∼110 pN, challenging the conventional view that helical proteins are mechanically weak. Dynamic force spectroscopy further revealed that the CTD becomes structurally unstable under acidic conditions (pH 5.7), reflecting its functional role in the spinning process. These findings advance our understanding of spider silk protein mechanics and provide new insights into the relationship between structure and mechanics.