The 20 amino acids

A Ala AlanineSmallHydrophobic

Helix: ++Strand: –Turn: – –

Mutate to Ala if you have to mutate but have no clue to which residue

C Cys CysteineSmallHydrophobicSulfur containing

Helix: –Strand: +Turn: +

The SH-group is very reactive:Can make Cys-Cys bridgesCan bind metal ions (especially Zn and Cu)

D Asp AspartateIntermediately largeHydrophilicNegatively charged

Helix: 0 (++ at N-terminus)Strands: – –Turn: ++

Often in active sitesCan bind ions (mainly calcium)

E Glu GlutamateLargeHydrophilicNegatively charged

Helix: ++Strand: 0Turn: –

F Phe PhenylalanineLargeHydrophobicAromatic

Helix: 0Strand: ++Turn: – –

G Gly GlycineSmallest residueNo side chain

Hydrophobicity undeterminedVery flexibleStar of the turn

Helix: – –Strand: –Turn: ++

H His HistidineLargeHydrophilicCharge (depending on the environment):

PositiveNeutral or Negative

No secondary structure preference

Often in active sitesCan bind metal ions (mainly Zn, Ni, Cu)

I Ile IsoleucineIntermediately largeHydrophobic

Helix: 0Strand: ++Turn: – –

K Lys LysineLargeHydrophilicPositively charged

Helix: ++Strand: –Turn: 0

Long, flexible side chain

L Leu LeucineIntermediately largeHydrophobic

Helix: ++Strand: +Turn: – –

M Met MethionineLargeHydrophobicSulfur containing

Helix: ++Strand: 0Turn: – –

Non-reactive sulfur which can bind metal ionsOften the first residue of the sequence

Intermediately largeHydrophilic

Helix: – –Strand: 0Turn: ++

Can bind ions (Ca) but not as well as its isosteric partner Asp

N Asn Asparagine

P Pro ProlineSmallHydrophobic

Helix: – – (except at the first position)Strand: – –Turn: ++

Imino acidNo backbone protonPre-bend for turns

Q Gln GlutamineLargeHydrophilic

Helix: +Strand: 0Turn: 0

Isosteric with Glu

LargeHydrophilicPositively charged

No secondary structure preference

Contains a rigid guanidinium group

R Arg Arginine

S Ser SerineSmallIntermediate hydrophobicityAlcoholic

Helix: –Strand: –Turn: ++

Often in active sites (with Asp and His)Can bind calcium

T Thr ThreonineSmallIntermediate hydrophobicityAlcoholic

Helix: 0Strand: +Turn: 0

Can bind calcium

V Val ValineSmallHydrophobic

Helix: 0Strand: ++Turn: – –

Isosteric with Thr

W Trp TryptophanLargest residueHydrophobicAromatic

Helix: 0Strand: ++Turn: 0

Most conserved residue

Y Tyr TyrosineLargeIntermediate hydrophobicityAromaticAlcoholic

Helix: –Strand: ++Turn: 0