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Globular proteins usually have ___ residues facing the interior (interact with one another) and ___ residues facing the exterior (reacting with the solvent).
Why is it important that the exterior of a globular protein has polar residues facing the exterior?
The interact with the solvent, making the protein soluble.
What is different about the interior of a protein?
It is more analogous to an organic solvent, thus, the pKas of side chains are perterbed
Specific combination of alpha helices and B sheets
Tell structural information
What are examples of a motif?
BAB - two antiparallel B, connected by and A
AA - two antiparallel As
B meander - Antiparallel sheets formed by series of tight reverse turns
Greek Key - repetitive structure (check out my ring!)
Calcium binding proteins are often enriched in? Why?
Asp, Glu, Ser, and Thr.
Are (-) so they attract the Ca2+ cation
Examples of a Beta Helix?
Pathogen (bacteria, virus, or toxin) proteins that bind the protein to the host cell.
Such as: Bordetella, ulcers, malaria, and anthrax
Fibrous proteins contain:
Tend to only have one type of secondary structure
Alpha OR Beta, but not both
What is the basic unit of alpha keratin?
Dimer of A-helices
Has high Cys content
PSEUDO 7-REPEAT WITH A AND D HYDROPHOBIC
What causes the alpha keratin in hair to be curly? What is the difference between a "permanent" and a "set" in curly hair?
Disulfide Bonds (remember, high Cys content)
Permanent - redox reaction rearranges disulfide bonds
Set - water rearranges H-bonds
What does Silk Fibroins consist of?
Antiparallel B-sheets aligned paralled to axis of fiber
Forms a microcrystalline array
Why is the sequencing of silk important?
All the Gly on one side and all the Ala/Ser on other side because B-sheet alternates residues!!
What is the composition of collagen?
3 L-handed helical chains interwoven to produce a R-handed superhelical
What is the unique sequence of the amino acid composition?
About 33% Glycine
About 30% Pro and HyPro together
Has a high level of non-standard amino acids
Why are Gly and Pro so important to collagen?
Only Gly is small enough to fit into the center
Pro permits the sharp twists
Collagen has unusual crosslinking between ___ and ___ which aids in strengthening the fibrils.
Lys and His
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