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Melanin

Group of signaling proteins made and released by host cells in response to pathogen (virus,bacteria,parasite tumor etc)

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Melanin

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  1. Melanin Production Mrs.N.Gunasheela Asst Professor,Dept of Microbiology, Sri Ramakrishna College of Arts & Science for Women, Coimbatore.

  2. Introduction • Melanin are a large, diverse family of light-absorbing biopolymers that aresynthesized by animals, plants, bacteria, and fungi. • Application • Topical sunscreens, sunlight-protective coatings for plastics, or additives for cosmetic products • Melanin are obtained in small quantities either by extraction from naturalsources or by chemical synthesis.

  3. Biochemical Analysis • Melanin are irregular, random polymers that are composed of indoles, benzothiazoles, and amino acids Copper –monooxygenase tyrosinase • Tyrosine dihydroxyphenylalanine quinone Final stages - polymerization of melanin are nonenzymatic Depending on the chemical nature of the non quinone components that are incorporated into the polymeric structure (typically hydroxylated organic compounds) End product can be black, brown, yellow, red, or violet

  4. Mechanism The genes involved in melanin biosynthesis in the bacteriumStreptomyces antibioticushave been isolated and analyzed. Two open reading frames (ORFs) tyrosinase ORF438(encoding a protein of unknown function) (molecular weight, 30,600) (molecular weight-14,800) Test whether both of these genes are required for melanin production Subcloned onto an E.coli expression vector

  5. Vector Amp R Amp R pBGC620.3 pBGC619 RBS2 Tyrosinase gene Tyrosinase Gene RBS1 ORF438 RBS1 P

  6. Synthesis Vector with the tyrosinase gene directed the synthesis of a larger amount of tyrosinase than did the vector containing both the tyrosinase and the ORF438 genes. However, the amount of tyrosinase was irrelevant, because it turned out that melanin biosynthesis required the products of both genes. The protein encoded by ORF438 may act as a copper donor to apotyrosinase, the inactive precursor form of tyrosinase. Apotyrosinases are activated by acquiring copper ions. Under natural conditions, after dihydroxyphenylalanine quinone is produced by tyrosinase, a variety of low-molecular-weight compounds (nonquinones) can be incorporated into the final polymer.

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