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Fibroin is an insoluble 
The silk worm produces fibroin with three chains, the light, heavy, and the glycoprotein P25. The heavy and light chains are linked by a disulphide bond, and P25 associates with disulphide-linked heavy and light chains by noncovalent interactions. P25 plays an important role in maintaining integrity of the complex.
The heavy fibroin protein consists of layers of antiparallel beta sheets. Its primary structure mainly consists of the recurrent
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
present in silk
Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the ...
produced by numerous insects, such as the larvae of ''Bombyx mori
The domestic silk moth (''Bombyx mori''), is an insect from the moth family Bombycidae. It is the closest relative of ''Bombyx mandarina'', the wild silk moth. The silkworm is the larva or caterpillar of a silk moth. It is an economically imp ...
'', and other moth genera such as ''Antheraea
''Antheraea'' is a moth genus belonging to the family Saturniidae. The genus was erected by Jacob Hübner in 1819. Several species of this genus have caterpillars which produce wild silk of commercial importance. Commonly called "tussar silk", t ...
'', '' Cricula'', '' Samia'' and '' Gonometa''. Silk in its raw state consists of two main proteins, sericin
Sericin is a protein created by ''Bombyx mori'' (silkworms) in the production of silk. Silk is a fibre produced by the silkworm in production of its cocoon. It consists mainly of two proteins, fibroin and sericin. Silk consists of 70–80% f ...
and fibroin, with a glue-like layer of sericin coating two singular filaments of fibroin called brins. Silk fibroin is considered a β-keratin
Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
related to proteins that form hair, skin, nails and connective tissues.
The silk worm produces fibroin with three chains, the light, heavy, and the glycoprotein P25. The heavy and light chains are linked by a disulphide bond, and P25 associates with disulphide-linked heavy and light chains by noncovalent interactions. P25 plays an important role in maintaining integrity of the complex.
The heavy fibroin protein consists of layers of antiparallel beta sheets. Its primary structure mainly consists of the recurrent amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...
sequence (Gly
Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid (carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinogeni ...
-Ser
Ser or SER may refer to:
Places
* Ser, a village in Bogdand Commune, Satu Mare County, Romania
* Serpens (Ser), an astronomical constellation of the northern hemisphere
* Serres, known as Ser in Serbian, a city in Macedonia, Greece
Organization ...
-Gly-Ala Ala, ALA, Alaa or Alae may refer to:
Places
* Ala, Hiiu County, Estonia, a village
* Ala, Valga County, Estonia, a village
* Ala, Alappuzha, Kerala, India, a village
* Ala, Iran, a village in Semnan Province
* Ala, Gotland, Sweden
* Alad, S ...
-Gly-Ala)''n''. The high glycine (and, to a lesser extent, alanine) content allows for tight packing of the sheets, which contributes to silk's rigid structure and tensile strength. A combination of stiffness and toughness make it a material with applications in several areas, including biomedicine
Biomedicine (also referred to as Western medicine, mainstream medicine or conventional medicine)
and textile
Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...
manufacture.
Fibroin is known to arrange itself in three structures, called silk I, II, and III. Silk I is the natural form of fibroin, as emitted from the ''Bombyx mori'' silk glands. Silk II refers to the arrangement of fibroin molecules in spun silk, which has greater strength and is often used in various commercial applications. Silk III is a newly discovered structure of fibroin. Silk III is formed principally in solutions of fibroin at an interface (i.e. air-water interface, water-oil interface, etc.).
Degradation
Many species of ''Amycolatopsis
''Amycolatopsis'' is a genus of high GC-content bacteria within the family Pseudonocardiaceae.
The genus is known for producing many types of antibiotics, including
* Epoxyquinomicin, related to ''Amycolatopsis sulphurea'', are a class of weak ...
'' and '' Saccharotrix'' bacteria are able to degrade both silk fibroin and polylactic acid.
References
{{InterPro content, IPR009911 Insect proteins Silk