THE MECHANISM OF SPIDER SILK PROTEIN SELF-ASSEMBLY INTO FIBER

Abstract

Elucidating the mechanism of silk formation is necessary for producing artificial silk fibers. NRPCMiSp, a miniature minor ampullate spidroin consisting of an N-terminal domain (NTD), a repetitive domain (RP), two linker domains (LK) and a C-terminal domain (CTD), was used to investigate silk protein assembly and silk fiber formation in this study. There are no significant interactions between domains in NRPCMiSp. Under the biological conditions, the oligomers can self-assemble into stable nanoparticles that further associate to form droplets. The droplets can form gel-like fibers through elongation. Only shear force mimicking the one in the spider spinning duct can produce fiber structures similar to those of the natural silk. The findings of this study favour the micelle theory and provide more details about structural and functional roles of the assemblies. Moreover, this study also presents a dynamic process of droplet formation that provides a link between protein assembly and silk fiber.