Definition for Valine
From Biology Forums Dictionary
One of the 20 naturally-occurring amino acids, valine has a β-branched, aliphatic side chain. Given the nonpolar nature of the valine side chain, it tends to occur in the interior of proteins, where it interacts favorably with other nonpolar side chains. The side chain of valine, like those of other amino acids with aliphatic side chains (alanine, leucine, and isoleucine), is unreactive under physiological conditions. Therefore, these residues are do not play catalytic roles and are not subject to posttranslational modifications. The purpose of these residues in proteins is mainly structural, their side chains packing together to form the hydrophobic core of the protein's tertiary structure.
Facts and Figures
Residue mass: 99.14
Frequency of occurrence in proteins: 6.6%
pKa values: α-COOH, 2.29; α-NH3+, 9.74.
Codons GUN (Note: N = any of the 4 bases)
Symbol: Val or V.