Assembly characteristics of plant keratin intermediate filaments in vitro

After selective extraction and purification, plant keratin intermediate filaments were reassembled in vitro. Scanning tunneling microscope (STM) and transmission electron microscope (TEM) micrographs showed that acidic keratins and basic keratins can assemble into dimers and further into 10 nm filaments in vitro. In higher magnification images, it can be seen that fully assembled plant keratin intermediate filaments consist of several thinner filaments of 3 nn in diameter, which indicates;the formation of protofilaments in the assembly processes. One of the explicit features of plant keratin intermediate filaments is a 24-25 nm periodic structural repeat alone the axis of both the 10 nm filaments and protofilaments. The periodic repeat is one of the fundamental characteristic of all intermediate filaments, and demonstrates the hall staggered arrangement of keratin molecules within the filaments.