Chapter 4: Translation and Protein Structure
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Special Amino Acids
Hydrophobic Amino Acids
Alanine (Ala, A)
Valine (Val, V)
Leucine (Leu, L)
Isoleucine (Ile, I)
Tyrosine (Tyr, Y)
Methionine (Met, M)
Tryptophan (Trp, W)
Phenylalanine (Phe, F)
Proline (Pro, P) #
Glycine (Gly, G) #
Cysteine (Cys, C) #
R Group is H, so symmetrical and Nonpolar
Increases flexibility of Polypeptide Backbone
R Group linked back to amino group
Creates kink in chain, restricts rotation of C-N bonds
Hydrophobic
Hydrophilic
--SH group - when two come into contact with each other form S-S disulfide bond. This bond forms cross-bridges that affects structure
Hydrophobic
Hydrophilic Amino Acids
Basic
Acidic
Polar
Glutamine (Gln, Q)
Serine (Ser, S)
Asparagine (Asn, N)
Threonine (Thr, T)
Arginine (Arg, R)
Lysine (Lys, K)
Histidine (His, H)
Aspartic acid (Asp, D)
Glutamic acid (Glu, E)
Protein Structure
Residues: Amino acids incorporated into proteins
Secondary Structure: Interactions between stretches of amino acids in a protein
Primary Structure: Sequence of amino acids in a protein
Tertiary Structure: Longer-range interactions between secondary structures- overall 3D shape of polypeptide
Quaternary Structure: Individual polypeptides that interact with each other
Results from hydrogen bonding in polypep backbone
Alpha helix: Tight right-handed coil
Beta sheet: Folds back on itself, forming pleated sheet-carbonyl and amide group across strands
Made up of several secondary structure combinations
Determines Function
Proteins can be Denatured (unfolded) by chemical or temperature changes
Chaperones: Proteins that protect slow-folding or denatured proteins until they attain their structure
Amino acids are ionic at physiological pH (Zwitterion); tetrahedral
Water is needed to break peptide bond
Peptide chains are synthesized starting at amino-terminal end, ending at carboxyl-terminal end