Described herein are recombinant integral membrane proteins having multiple transmembrane domains that have been engineered to be less hydrophobic, through alteration of the amino acid sequence of the native protein, but retain the ability to bind their natural ligand. The decreased hydrophobicity of the described proteins makes them more water soluble than the native protein, which allows the described proteins to be expressed in bacteria in large quantities and isolated in the absence of membranes, all while retaining the ability to interact with known ligands.