Structure of the disulfide‐rich modules of a striking tandem repeat protein, avian cysteine‐rich eggshell membrane protein

Abstract Avian eggshell membrane (ESM) is fabricated within the isthmus region of the oviduct and is comprised of three juxtaposed, predominantly proteinaceous layers lying between egg white and the calcified shell. The limiting membrane is less than 0.5 μm in thickness and forms the osmotic barrier for the egg. This first layer provides the foundation for the successive deposition of two mats of protein fibers. Fibers from both inner and outer layers appear to have similar amino acid compositions and