Terms in this set (20)Amino Acid,∆∆∆∆
Glycine
Not Chiral
Nonessential
Nonpolar
(Structure) High Conformational Flexibility
(Function) Sidechain-less backbone (bind to phosphates)
Alanine
Nonessential
Nonpolar
Structure (Present in most non-critical protein contexts)
Function (Very non-reactive, substrate recognition or specificity)
Proline
Nonessential
Nonpolar
Side chain connected to backbone twice
Secondary Amine (Imino acid) (S stereochemistry)
(Structure) Very limited in conformations, usually found on the protein surface
(Function) Important roles in molecular recognition
Valine
Essential
Nonpolar
(Structure) Bulkiness near the protein backbone. Hydrophobic: prefers to be buried in protein hydrophobic cores
(Function) Very non-reactive, substrate recognition in hydrophobic amino acids and lipids
Leucine
Essential
Nonpolar
(Structure): Hydrophobic prefers to be buried in protein hydrophobic cores. Preference for a helices more than in B strands
(Function) Very non-reactive, substrate recognition
Isoleucine
Essential
Nonpolar
(Structure) Bulkiness near to the protein backbone. Hydrophobic prefers to be buried in hydrophobic cores
(Function) Very non-reactive, substrate recognition
Methionine
Essential, sulfur atom
Nonpolar
(Structure) Slightly nonpolar thioester group. Prefers to be buried in a protein hydrophobic cores
(Function) Fairly non reactive; first amino acid in proteins
Substrate recognition, Can be involved in binding to atoms such as metals
Phenylaline
Aromatic
Essential
Nonpolar
(Structure) Prefers to be buried in protein hydrophobic cores, aromatic side chain can also mean that is involved in stacking interactions with other aromatic side chains
(Function) Fairly non-reactive, substrate recognition, Interactions with non-protein ligands
Tryosine
Aromatic
Nonessential
Polar
(Structure) Prefers to be buried in protein hydrophobic cores. Aromatic side chain can also mean that it is involved in stacking interactions with other aromatic side chains.
(Function) Reactive hydroxyl group. Substrate recognition
Tryptophan
Aromatic
Essential
Hydrophobic
(Structure) Prefers to be buried in protein hydrophobic cores. Aromatic side chain can also mean that is involved in stacking interactions with other aromatic side chains.
(Function) Nitrogen in aromatic system. Substrate recognition
Serine
Polar
Nonessential
Small
(Structure) Conformationally versatile
(Function) The hydroxyl group is fairly reactive. Common in functional centers (for catalysis), catalytic triad found in many hydrolyses, site of phosphorylation
Threonine
Polar
Essential
Small
2 chiral centers
(Structure) Conformationally versatile
(Function) The hydroxyl group is fairly reactive, common in functional centers, site of phosphorylation and or glycosylation
Cysteine
Polar
Semi-essential
Small
(Structure) Extracellular proteins: frequently involved in disulphide bonds (pairs of cysteines are oxidized to form a covalent bond). Intracellular: Sulfydryl side-chain is excellent for binding to metals, such as zinc
(Function) The sulfur group is reactive (nucleophile)
Asparagine
Polar
Nonessential
Amido of aspartate
(Structure) Surface of proteins, exposed to an aqueous environment
(Function) Frequently involved in protein active or binding sites
Glutamine
Polar
Nonessential
Amido of glutamate
(Structure) Surface of proteins; exposed to an aqueous environment
(Function) Frequently involved in protein active or binding sites
Lysine
Positively Charged
Essential
(Structure) Prefers to be on the outside of proteins, hydrophobic side chains, terminated with positive charge
(Function) Involved in salt bridges, binds nucleic acids, site of post-translational modifications
Arginine
Positively Charged
Semi-essential
(Structure) Generally prefer to be on the outside of proteins. Hydrophobic side chain, terminated with positive charge.
(Function) Frequently involved in salt bridges, binds nucleic acids, complex quanidinium group
Histidine
Positively Charged
Essential
Imidazole
(Structure) pKa near to that of physiological pH
(Function) Relatively small shifts in pH change its average charge
• Most common amino acids in active or binding sites
• Common in metal binding sites (e.g. zinc)
• Charge relay systems (such as catalytic triads in proteases)
Glutamate
Negatively charged
Non-essential
(Structure) Prefer to be on the surface of proteins
• When buried in protein: salt-bridges (Arg)
(Function) Frequently involved in protein active or binding sites
• Interact with positively charged atoms (e.g. zinc
Aspartate
Negatively charged
Non-essential
(Structure) Prefer to be on the surface of proteins
• When buried in protein: salt-bridges (Arg)
(Function) Frequently involved in protein active or binding sites
• Interact with positively charged atoms (e.g. zinc)
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