Describe the properties of the following amino acids at pH 7

Describe the properties of the following amino acids at pH 7: proline, phenylalanine and lysine. Include in your answer where they are most likely to be found in the structure of globular proteins and why.

Solution

PART 1 ANSWER:

Properties of Proline:

1) It is an nonpolar, alpha amino acid

2) It has an secondary amine group

3) Has an exceptional conformational rigidity

Properties of Phenylalanine:

1) An essential alpha amino acid, it is neutral and non polar in nature

2) It is a derivative of alanine where phenyl group takes the place of hydrogens on the CH3 group.

3) Has very strong hydrophobic property

Properties of Lysine:

1) An essential amiono acid, has positively charged e- amino group.

2) Because of the amino grp it has high pKa value

3) 3 methylene groups in the side chain makes lysine hydrophobic in nature

PART 2 ANSWER:

1) Proline has N -end amine group which forces CO-NH sequence into fixed conformation, it disrupts the alpha helix and beta sheet structure, Proline is found in collagen which it undergoes translational modification and makes hydroxy proline to stabilize the structure of collagen.

2) Phenylalanine tend to orient towards the interior of the protein because of the hydrophobic nature and rigid aromatic gruop in the side chain.

3) Lysine has strong +ve charge so it tends to be located on the outer phydrophilic surface of the globular protein, if found inside lysine is paired with -vely charged amino acid e.g glutamate.