Protein Tertiary and Quaternary Structures
Fibrous
Polypeptide chains in long strands or sheets
Globins
Polypeptide chains in a spherical or globular shape
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support, shape, external protection
Insoluble in water
alpha-keratin
High concentration of hydrophobic amino acid residues both in interior of protein and on surface
hair, wool, claws, nails, hooves, much of outer layer of skin
Right handed alpha helix
Two strands wrapped around each other to form a super twisted coiled coil
Rich in hydrophobic residues, because the part where the two helices touch is made up of these
Cross links stabilizing quaternary structure are disulfide bonds
Hair can be curled when reduced---breaking disulfide bonds, then reoxidized, reforming disulfide bonds
Silk
B sheets--rich in gly and ala residues
Collagen
connective tissue like tendons, cartilage, cornea of eye
Unique secondary structure
coiled coil, but one with three separate polypeptides, called alpha chains, twisted around one another
Usually in Pro-X-Y conformation, where X is usually Pro and Y is usually 4-Hyp. in the absence of vitamin C, cells can't hydroxylate at the Y positions