Lec12 - Silk: the most elegant -sheet Animals that produce...

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Silk: the most elegant β -sheet Animals that produce silk like substance Silkworm (Bombix mori) Silk is strong and flexible
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Fibroin is a stack of β sheets
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β -sheet is stabilized by backbone hydrogen bonds
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β bulge An aa that is not H-bonded to the neighboring strand
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Fibrous proteins Dominated by a single type of secondary structure Protective, connective or supportive Keratin Fibroin Collagen
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α Keratin Skin, hair, horn, feathers
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Coiled coil
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α -keratin a coiled coil Two α -helices (right-handed) Parallel Left handed coiled coil The pitch is 5.1 Å (instead of 5.4 Å) Stabilized by hydrophobic interactions 7 residues pseudo-repeat a-b-c-d-e-f-g in which a and d are hydrophobic
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Two helices in keratin are kept together as a consequence of hydrophobic interactions
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The fibroin sequence is very simple (-Gly-Ala-Gly-Ser-Gly-Ala-Gly-Ala-) n
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Collagen Fibrous Highly elongated Single type of secondary structure - helix
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Collagen is the most abundant vertebrate protein Found in all tissues Extracellular matrix Provides strength to bone, cartilage, tendons skin and blood vessels
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30 collagen genes 19 different kinds of collagen protein Type I – two α 1 chains and one α 2 chain 14 Å wide 3000 Å long
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Lec12 - Silk: the most elegant -sheet Animals that produce...

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