Water-soluble trans-membrane proteins and methods for the preparation and use thereof

A method for producing a water-soluble variant of a G Protein-Coupled Receptor (GPCR), the method comprising:

• (1) entering a sequence of the GPCR for analysis;
• (2) obtaining a variant of the GPCR, wherein substantially all of Leucine (L), Isoleucine (I), Valine (V), and Phenylalanine (F) in the transmembrane (TM) domain alpha-helical segments (“TM regions”) of the GPCR are substituted, wherein:
• (a)
• each said Leucine (L) is independently substituted by Glutamine (Q), Asparagine (N), or Serine (S);
• (b) each said Isoleucine (I) and said Valine (V) are independently substituted by Threonine (T), Asparagine (N), or Serine (S);
• and,
• (c) each said Phenylalanine is substituted by Tyrosine (Y);
• and, subsequently,
• (3) obtaining an α-helical secondary structure result for the variant to verify maintenance of α-helical secondary structures in the variant;
• (4) obtaining a trans-membrane (TM) region result for the variant to verify water solubility of the variant, wherein said water solubility of said variant is verified when said TM region result predicts absence of TM regions or low propensity to form TM regions, based on the sequence of said variant, and,
• (5) selecting and producing the variant obtained in step (2) that has maintained α-helical secondary structures according to step (3), and is verified to have water solubility in step (4) as said water-soluble variant of the GPCR.