Synthesis of a genetically engineered repetitive polypeptide containing periodic selenomethionine residues

Genetically engineered proteins will play an important role in materials science. Many natural proteins have excellent materials properties such as the silks, elastin, and collagen, and, in principle, both these and entirely new protein materials can be produced from artificial genes. Good early progress has been made in this direction, including the synthesis of repetitive proteins predicted to self-assemble into solid lamellae of defined thickness and surface function (refs 1 and 2 and references therein). While biological synthesis offers the materials scientist superior control over polymer chain architecture, including purity of sequence, size, and stereochemistry, its versatility is limited to the 20 amino acids that appear in natural proteins. Thus, an important aim for the future will be to expand the number of amino acids that can be utilized in protein biosynthesis. First efforts in this direction would logically start with amino acid analogs known to be incorporated during translation. We describe here the first genetic synthesis of a periodic protein material in which an amino acid analog, selenomethionine, completely replaces a natural amino acid