Effect of amino acid mutations on ligand binding to the hMT2 melatonin receptor
Amino acids are represented in single-letter code with position number shown. Superscripts after the second amino acid indicate that the substituted amino acid represents the amino acid in the designated receptor at the analogous position. The position in the transmembrane domain is indicated using the numbering scheme of Ballesteros and Weinstein (1995).
| Amino Acid Mutation Scheme | TM No. | Expression System | Characterization | Reference |
|---|---|---|---|---|
| Human | ||||
| G24E | NTerm | COS-7 | Heterozygous polymorphism with no phenotype. When expressed in COS-7 cells no change in Kd or Ki with melatonin. | Ebisawa et al., 2000 |
| L66F | 1.58 | COS-7 | Heterozygous polymorphism with no phenotype. | Ebisawa et al., 2000 |
| C113A | ECL1 | HEK293 | No specific binding. | Mseeh et al., 2002 |
| C140A | ICL2 | HEK293 | No change in Kd, slightly increased Ki for melatonin (1.6×), decreased Bmax (22×). | Mseeh et al., 2002 |
| C143A | ICL2 | HEK293 | No change in Kd, slightly increased Ki for melatonin (1.4×), slightly increased Bmax (1.8×). | Mseeh et al., 2002 |
| C190A | ECL2 | HEK293 | No specific binding. | Mseeh et al., 2002 |
| C219A | 5.57 | HEK293 | No change in Kd or Ki. Decreased Bmax (5×). | Mseeh et al., 2002 |
| C263A | 6.47 | HEK293 | No change in Kd or Ki. Decreased Bmax (31×). | Mseeh et al., 2002 |
| C302A | 7.47 | HEK293 | No change in Kd or Ki. Decreased Bmax (4×). | Mseeh et al., 2002 |
| S123A | 3.35 | HEK293 | No change in Kd or Ki. Decreased Bmax (5×). | Gerdin et al., 2003 |
| S127A | 3.39 | HEK293 | No change in Kd or Ki. Decreased Bmax (3×). | Gerdin et al., 2003 |
| N175Aa | 4.60 | HEK293 | No change in Kd, slightly increased Ki for melatonin. No change in Bmax. | Gerdin et al., 2003 |
| H208Aa | 5.46 | HEK293 | Increased Kd and Ki for melatonin. No change in Bmax. | Gerdin et al., 2003 |
| F257A | 6.41 | HEK293 | No change in Kd or Ki. No change in Bmax. | Gerdin et al., 2003 |
| W264A | 6.48 | HEK293 | Decreased Kd, no change in Ki. Decreased Bmax (22×). | Gerdin et al., 2003 |
| S293A | 7.38 | HEK293 | No change in Kd or Ki. No change in Bmax. | Gerdin et al., 2003 |
| V204Aa | 5.42 | HEK293 | No specific binding. | Mazna et al., 2004 |
| V205 | 5.43 | HEK293 | No change in Kd. No change in Bmax. | Mazna et al., 2004 |
| F209A | 5.47 | HEK293 | No change in Kd. Decreased Bmax. No change in Ki for melatonin, luzindole or 4P-PDOT. | Mazna et al., 2004 |
| G271T | 6.55 | HEK293 | Not saturable. | Mazna et al., 2004 |
| L272Aa | 6.56 | HEK293 | No specific binding. | Mazna et al., 2004 |
| Y298Aa | 7.43 | HEK293 | No specific binding. | Mazna et al., 2004 |
| M120A | 3.32 | HEK293 | No change in Kd or Bmax. | Mazna et al., 2005 |
| G121A | 3.33 | HEK293 | No change in Kd or Bmax. | Mazna et al., 2005 |
| G121I | 3.33 | HEK293 | No change in Kd or Bmax. | Mazna et al., 2005 |
| V124A | 3.36 | HEK293 | No change in Kd with decreased Bmax. | Mazna et al., 2005 |
| I125A | 3.37 | HEK293 | No change in Kd or Bmax. | Mazna et al., 2005 |
| Y188A | ECL2 | HEK293 | No specific binding. | Mazna et al., 2005 |
| Y188F | ECL2 | HEK293 | No specific binding. | Mazna et al., 2005 |
| N268Aa | 6.52 | HEK293 | No specific binding. | Mazna et al., 2005 |
| N268Da | 6.52 | HEK293 | No specific binding. | Mazna et al., 2005 |
| N268La | 6.52 | HEK293 | No specific binding. | Mazna et al., 2005 |
| N268Qa | 6.52 | HEK293 | No change in Kd or Bmax. | Mazna et al., 2005 |
| A275I | 6.59 | HEK293 | No specific binding. | Mazna et al., 2005 |
| A275Va | 6.59 | HEK293 | No change in Kd or Bmax. | Mazna et al., 2005 |
| V291Aa | 7.36 | HEK293 | No specific binding. | Mazna et al., 2005 |
| V291Ia | 7.36 | HEK293 | No specific binding. | Mazna et al., 2005 |
| L295Aa | 7.40 | HEK293 | No specific binding. | Mazna et al., 2005 |
| L295Ia | 7.40 | HEK293 | No specific binding. | Mazna et al., 2005 |
| L295Va | 7.40 | HEK293 | No specific binding. | Mazna et al., 2005 |
| Hamster | ||||
| P41A | 1.33 | CHO-K1 | No change in Kd or Bmax. No change in EC50 or Emax for melatonin or 2-iodomelatonin stimulation of GTPγ35S binding. | Mazna et al., 2008 |
| P93A | 2.57 | CHO-K1 | No change in Kd or Bmax. No change in EC50 or Emax for melatonin or 2-iodomelatonin stimulation of GTPγ35S binding. | Mazna et al., 2008 |
| P95A | 2.59 | CHO-K1 | No change in Kd or Bmax. No change in EC50 or Emax for melatonin or 2-iodomelatonin stimulation of GTPγ35S binding. | Mazna et al., 2008 |
| P158A | 4.40 | CHO-K1 | No change in Kd or Bmax. No change in EC50 or Emax for melatonin or 2-iodomelatonin stimulation of GTPγ35S binding. | Mazna et al., 2008 |
| P174A | 4.59 | CHO-K1 | No specific binding. | Mazna et al., 2008 |
| P174G | 4.59 | CHO-K1 | No specific binding. | Mazna et al., 2008 |
| P212A | 5.50 | CHO-K1 | No change in Kd or Bmax. Decreased Emax for melatonin and 2-iodomelatonin, stimulation of GTPγ35S binding. | Mazna et al., 2008 |
| P212G | 5.50 | CHO-K1 | No change in Kd or Bmax. Increased EC50 for 2-iodomelatonin stimulation of GTPγ35S binding with no change in Emax. | Mazna et al., 2008 |
| P266A | 6.50 | CHO-K1 | No specific binding. | Mazna et al., 2008 |
| P266G | 6.50 | CHO-K1 | No specific binding. | Mazna et al., 2008 |
| A305P | 7.50 | CHO-K1 | No specific binding. | Mazna et al., 2008 |
| A305V | 7.50 | CHO-K1 | No change for Kd or Bmax. Increased EC50 for melatonin and 2-iodomelatonin stimulation of GTPγ35S binding with decreased Emax. | Mazna et al., 2008 |
HEK, human embryonic kidney; CHO, Chinese hamster ovary.
↵a Amino acid residues important for modulating binding to the MT1 receptor (Farce et al., 2008).