Table 1.

Amino Acid Design Elements^a

position in water	function in water, high pH	function in membrane, low pH	amino acid choice
a	helical bundle hydrophobic core	membrane-facing	Leu
b	solvent-exposed, imparts solubility	small residue for helical interface, potential interhelical hydrogen bonding	Ser
c	solvent-exposed, imparts solubility	trigger residue, changes protonation state/hydrophobicity at low pH; potential interhelical hydrogen bonding	Asp, Glu, His
d	helical bundle hydrophobic core	membrane-facing	Leu
e	modulation of helical propensity	small residue for helical interface	Ala
f	solvent-exposed, imparts solubility	solvent-exposed in channel state (inner channel lining); imparts folds specificity by encoding helical orientation preference	Lys, Gln
g	modulation of helical propensity	small residue for helical interface	Ala, Gly

^aRefer to Figure 3 for corresponding helical description.