Flashcards in protein structure and function Deck (43)
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1
Examples of Silk Proteins
1. Collagen
2. Elastin
3. Keratin
4. Silk Fibroin
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▪ insoluble, extracellular (found outside the cell)
Collagen
3
▪ very strong due to aldol crosslinks (covalent bond)
▪ found in all animals
Collagen
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▪ most abundant in the human body
Collagen
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▪ essential in all connective tissues e.g. cartilage, bone, tendons, ligaments, and skin
Collagen
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▪ triple helical structure (tropocollagen) stabilized by
aldol crosslinks
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▪primary structure of collagen
repeating tripeptide (Gly-X-Y) where X is usually Pro and Y is usually hydroxyproline
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they also exhibit H-bonding because of hydroxyproline
Collagen
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they are not α-helical; just helical
Collagen
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– excessive collagen synthesis
Fibrosis
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▪ overproduction of type 1 collagen in lungs reduces the lung’s ability to expand for air intake and interferes with normal breathing; scarring of lungs
Pulmonary fibrosis
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▪ excessive deposition in liver leads to scar tissue formation due to overconsumption of alcohol; may lead to cirrhosis
Liver fibrosis
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caused by insufficient collagen production where skin and tendons are weak and easily stretched producing loose joints and hyperextensive limbs
Ehler’s-Danlos (Rubberman syndrome)
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▪ type 1 procollagen molecules fail partially or completely to assemble into triple helices and are therefore degraded.
▪ reduced amount of collagen leads to fragile bones; easily fractured
Osteogenesis Imperfecta (Brittle bone syndrome)
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▪ found predominantly in walls of arteries, lungs, intestines, skins, etc.
Elastin
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▪ structural proteins that gives elasticity to the body’s tissues and organs
Elastin
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MW of elastin
72 kDA
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AAs in elastin
Small nonpolar
A,V, L,G
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▪WHY hydrophobic elastin molecules “slide and stretch” over one another
to maintain structural integrity and provide recoil
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▪ elastin protein molecules are crosslinked by WHAT TYPE OF BONDS
covalent bonds
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tough, fibrous, insoluble protein that makes up the skin, hair and nails
KERATIN
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also found in claws, hooves, feathers and horns
KERATIN
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human hair is __% cysteine;
14
24
the more disulfide bridges present, the _ curly
more
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Soft Keratin –____disulfide bonds
Hard Keratin – ____disulfide bonds
soft - less
hard-more
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-most abundant protein in vertebrates
-has 3 polypeptide chains wrapped around each other in a ropelike twist or triple helix
collagen
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collagen fibers are both intra and intermolecularly linked by covalent bonds formed by reactions of ______ residues
lysine and histidine
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side chains of collagen are on the __ of the triple-helical molecule
surface
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in collagen, the AA which facilitates formation of the helical conformation of each alpha chain because it causes kinks
Proline
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