Hydrophobicity of proteins

Tony Day (tday@netcom.com)
Thu, 1 Feb 1996 08:44:42 -0700

Here's my $0.02 on the most and least hydrophobic residue.

1. Most hydrophobic is Ile. Of the residues with no polar side groups,
ile has the greatest surface area and ties for largest volume. Thus, I
would expect the side chain of ile to be least soluble in water.

2. I would suggest asp as the least hydrophobic residue. It has the
highest ratio of charged (-C02 -) to hydrophobic (-CH2-) moities.

3. The most hydrophilic residue in the tables that I can find is either
Arg (tables based on properties) or Lys (based on statistical occurence on
protein surfaces).

I think that whether or not these are 'right' answers must depend to some
extent on the use to which the results are to be put. For example lysine
has 3 methylene carbons. These can all make hydrophobic packing
interactions. If one were to mutate a lysine in which the amino group is
solvent exposed and the methylene groups are involved in packing, the best
substitution might be methionine. In this particular instance, tables of
chemical group hydrophobicity may be more relevant than amino acid