Re: what is the chemical compostion of silk. what are the amino acid involved

Silk is a proteinaceous filament produced in the posterior silk glands of the larva of the silkmoth (Bombyx mori), also called the silkworm. The silk filament is composed of a thread-like protein called fibroin, which is bundled and arranged lengthwise to form a continuous fiber. Fibroin is composed of two subunits, Fibroin Heavy Chain and Fibroin Light Chain, which are held together covalently (via disulfide bonds). The protein sequences of each subunit can be found by clicking on each fo the following links:

AAF76983 - fibroin heavy chain Fib-H [Bombyx mori]

CAA35180 - silk fibroin light chain [ Bombyx mori]

The heavy chain contains the major structural component that gives silk it characteristics. The structure of the heavy chain is composed of long fiber domains made up of repeats of the amino acid sequence, -GLY-SER-GLY-ALA-GLY-ALA- (-GSGAGA-)_N, where GLY (G) is glycine, SER (S) is serine, and ALA (A) is alanine. These stretches are interrupted by short bulkier stretches in which the serine is replaced by tyrosine, TYR (Y). The end of the heavy chain forms an globular region with the light chain, and this region is responsible for interactions with other fibroin molecules to give the silk its structural strength.