Self-assembly of cricoid proteins induced by "soft nanoparticles": an approach to design multienzyme-cooperative antioxidative systems.

A strategy to construct high-ordered protein nanowires by electrostatic assembly of cricoid proteins and "soft nanoparticles" was developed. Poly(amido amine) (PAMAM) dendrimers on high generation that have been shown to be near-globular macromolecules with all of the amino groups distributing throughout the surface were ideal electropositive "soft nanoparticles" to induce electrostatic assembly of electronegative cricoid proteins. Atomic force microscopy and transmission electron microscopy all showed that one "soft nanoparticle" (generation 5 PAMAM, PD5) could electrostatically interact with two cricoid proteins (stable protein one, SP1) in an opposite orientation to form sandwich structure, further leading to self-assembled protein nanowires. The designed nanostructures could act as versatile scaffolds to develop multienzyme-cooperative antioxidative systems. By means of inducing catalytic selenocysteine and manganese porphyrin to SP1 and PD5, respectively, we successfully designed antioxidative protein nanowires with both excellent glutathione peroxidase and superoxide dismutase activities. Also, the introduction of selenocysteine and manganese porphyrin did not affect the assembly morphologies. Moreover, this multienzyme-cooperative antioxidative system exhibited excellent biological effect and low cell cytotoxicity.