Recently, there has been growing interest in harnessing genetically engineered polymers to develop responsive biomaterials, such as hydrogels. Unlike their synthetic counterparts, genetically engineered polymers are produced without the use of toxic reagents and can easily be programmed to incorporate desirable hydrogel properties, including bioactivity, biodegradability, and monodispersity. Herein, we report the development of a copolymeric hydrogel that is based on the calcium-dependent protein, calmodulin (CaM). For our system, CaM and M13, a CaM-binding peptide, were incorporated into genetically engineered polymers with intervening linkers containing cleavable sequences. Spectroscopic and multiple-particle tracking (MPT) studies demonstrate that these polymers self-assemble through calcium-stabilized, noncovalent crosslinking to form a soft viscoelastic material. MPT further revealed that gelation is concentration-dependent. Collagenase digests show that the protein polymers are selectively degraded through specific cleavage. The modularity and stimuli-responsiveness of this system suggest its potential as a flexible scaffold for biomedical applications.