Proline, Serine/Threonine, Silk, Silkworm, Three consecutive AAs (chromophore formation)
by
0

Sericin is a protein created by Bombyx mori (silkworms) in the production of silk

A schematic illustration of silk fibers produced by silkworms: (A) the raw silk fiber is composed of two fibroin fibers held together with sericin covered with a protein coat. After degumming, the removal of sericin, the fibroin fibers are dissolved in solution; (B) the illustration of β-sheet crystallite embedded in the amorphous matrix of silk fibroin fibers; and (C) each silk fibroin heavy chain (H-chain) consists of hydrophobic and hydrophilic repetitive domains. F. Costa, … A.R. Boccaccini, in Peptides and Proteins as Biomaterials for Tissue Regeneration and Repair, 2018 Reprinted with permission from Jao D, Mou X, Hu X. Tissue regeneration: a silk road. J Funct Biomater 2016;7.

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% fibroin and 20–30% sericin; fibroin being the structural center of the silk, and sericin being the gum coating the fibres and allowing them to stick to each other.

Structure

Sericin is composed of 18 different amino acids, of which 32% is serine. The secondary structure is usually a random coil, but it can also be easily converted into a β-sheet conformation, via repeated moisture absorption and mechanical stretching. The serine hydrogen bonds give its glue-like quality. The genes encoding sericin proteins have been sequenced. Its C-terminal part contains many serine-rich repeats.

  • Garel A, Deleage G, Prudhomme JC (May 1997). “Structure and organization of the Bombyx mori sericin 1 gene and of the sericins 1 deduced from the sequence of the Ser 1B cDNA”. Insect Biochemistry and Molecular Biology. 27 (5): 469–77. doi:10.1016/S0965-1748(97)00022-2. PMID 9219370.
  • Takasu Y, Yamada H, Tamura T, Sezutsu H, Mita K, Tsubouchi K (November 2007). “Identification and characterization of a novel sericin gene expressed in the anterior middle silk gland of the silkworm Bombyx mori”. Insect Biochemistry and Molecular Biology. 37 (11): 1234–40. doi:10.1016/j.ibmb.2007.07.009. PMID 17916509.
  • Kludkiewicz B, Takasu Y, Fedic R, Tamura T, Sehnal F, Zurovec M (December 2009). “Structure and expression of the silk adhesive protein Ser2 in Bombyx mori”. Insect Biochemistry and Molecular Biology. 39 (12): 938–46. doi:10.1016/j.ibmb.2009.11.005. PMID 19995605.
This guy again…Hermann Emil Louis Fischer (1852 –1919) was a German chemist and 1902 recipient of the Nobel Prize in Chemistry. He discovered the Fischer esterification. He also developed the Fischer projection, a symbolic way of drawing asymmetric carbon atoms. He also hypothesized lock and key mechanism of enzyme action. He never used his first given name, and was known throughout his life simply as Emil Fischer.

Serine is one of the proteinogenic amino acids. Only the L–stereoisomer appears naturally in proteins. It is not essential to the human diet, since it is synthesized in the body from other metabolites, including glycine. Serine was first obtained from silk protein, a particularly rich source, in 1865 by Emil Cramer.[Cramer, Emil (1865). “Ueber die Bestandtheile der Seide” [On the constituents of silk]. Journal für praktische Chemie (in German). 96: 76–98. Serine is named on p. 93: “Ich werde den in Frage stehenden Körper unter dem Namen Serin beschreiben.” (I will describe the body [i.e., substance] in question by the name “serine”.)] Its name is derived from the Latin for silk, sericum. Serine’s structure was established in 1902.[Fischer, Emil; Leuchs, Hermann (1902). “Synthese des Serins, der l-Glucosaminsäure und anderer Oxyaminosäuren” [Synthesis of serine, of l-glucosaminic acid, and other oxyamino acids]. Berichte der Deutschen Chemischen Gesellschaft (in German). 35 (3): 3787–3805. doi:10.1002/cber.190203503213.][“Serine”. The Columbia Encyclopedia 6th ed. encyclopedia.com. Retrieved 22 October 2012.]

Using gamma ray examination, it was determined that sericin fibers are composed typically of three layers, all with fibers running in different patterns of directionality. The innermost layer, typically is composed of longitudinally running fibers, the middle layer is composed of cross fiber directional patterned fibers, and the outer layer consists of fiber directional fibers. The overall structure can also vary based on temperature, whereas the lower the temperature, there were typically more β-sheet conformations than random amorphous coils.

There are also three different types of sericin, which make up the layers found on top of the fibroin.

Sericin A, which is insoluble in water, is the outermost layer, and contains approximately 17% nitrogen, along with amino acids such as serine, threonine, aspartic acid, and glycine.

Sericin B, composed the middle layer and is nearly the same as sericin A, but also contains tryptophan.

Sericin C is the innermost layer, the layer that comes closest to and is adjacent to fibroin. Also insoluble in water, sericin C can be separated from the fibroin via the addition of a hot, weak acid. Sericin C also contains the amino acids present in B, along with the addition of proline.

Applications

Sericin has also been used in medicine and cosmetics. Due to its elasticity and tensile strength, along with a natural affinity for keratin, sericin is primarily used in medicine for wound suturing. It also has a natural infection resistance, and is used variably due to excellent biocompatibility, and thus is used commonly as a wound coagulant as well.

When used in cosmetics, sericin has been found to improve skin elasticity and several anti-aging factors, including an anti-wrinkle property. This is done by minimizing water loss from the skin. To determine this, scientists ran several experimental procedures, including a hydroxyproline assay, impedance measurements, water loss from the epidermis and scanning electron microscopy to analyze the rigidity and dryness of the skin. The presence of sericin increases hydroxyproline in the stratum corneum, which in turn, decreases skin impedance, thus increasing skin moisture. Adding in pluronic and carbopol, two other ingredients that can be included in sericin gels, performs the action of repairing natural moisture factors (NMF), along with minimizing water loss and in turn, improving skin moisture.

See also

References

  1. “Sericin”. Cytokines and Cells Online Pathfinder Encyclopedia. January 2008. Retrieved 27 April 2012.
  2. Padamwar MN, Pawar AP (April 2004). “Silk sericin and its applications: A review” (PDF). Journal of Scientific & Industrial Research. 63 (4): 323–329.
  3. Garel A, Deleage G, Prudhomme JC (May 1997). “Structure and organization of the Bombyx mori sericin 1 gene and of the sericins 1 deduced from the sequence of the Ser 1B cDNA”. Insect Biochemistry and Molecular Biology. 27 (5): 469–77. doi:10.1016/S0965-1748(97)00022-2. PMID 9219370.
  4. Takasu Y, Yamada H, Tamura T, Sezutsu H, Mita K, Tsubouchi K (November 2007). “Identification and characterization of a novel sericin gene expressed in the anterior middle silk gland of the silkworm Bombyx mori”. Insect Biochemistry and Molecular Biology. 37 (11): 1234–40. doi:10.1016/j.ibmb.2007.07.009. PMID 17916509.
  5. Kludkiewicz B, Takasu Y, Fedic R, Tamura T, Sehnal F, Zurovec M (December 2009). “Structure and expression of the silk adhesive protein Ser2 in Bombyx mori”. Insect Biochemistry and Molecular Biology. 39 (12): 938–46. doi:10.1016/j.ibmb.2009.11.005. PMID 19995605.
  6. Ersel M, Uyanikgil Y, Karbek Akarca F, Ozcete E, Altunci YA, Karabey F, Cavusoglu T, Meral A, Yigitturk G, Oyku Cetin E (April 2016). “Effects of Silk Sericin on Incision Wound Healing in a Dorsal Skin Flap Wound Healing Rat Model”. Medical Science Monitor. 22: 1064–78. doi:10.12659/msm.897981. PMC 4822939. PMID 27032876.

Categories: 

///

Post a Comment

Your email address will not be published. Required fields are marked *