The three branched-chain amino acids (BCAAs) are the most hydrophobic of the amino
acids and play crucial roles in determining the structures of globular proteins as well as the
interaction of the transmembrane domains of membranous proteins with phospholipid
bilayers. However, the three BCAAs do not behave identically. In terms of protein secondary
structure, valine and isoleucine exhibit a definite preference for the β-structure, whereas
leucine has a higher preference for the α-helix. Although mutation of one BCAA to another is …