Engineering of a synthetic silk protein. The future objective of silk engineering might not be to prepare identical copies of natural silks, but rather to capture its key structural and functional features in designs. The soluble synthetic silk should be able to assemble into protein fibers with desired properties, which includes the possibility to specifically functionalize the fiber surface e.g. by chemical cross-linking with biologically or chemically active groups. Synthetic silk engineering could be accomplished by assembling modules either originating from authentic genes, mimicking silk motifs or being entirely synthetic with defined functionality. The follow-up strategy would be to modify the resulting monomeric soluble protein either with the desired functionality prior to assembly into fibers, or to incorporate a reactive group that will subsequently permit the conjunction with desired functionality after the fibers have assembled.