Effect of amino acid mutations on ligand binding to the MT1 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. | Species | Expression System | Characterization | Reference |
|---|---|---|---|---|---|
| R54W | (1.59) | Human | COS cells | Heterozygous polymorphism with no phenotype. Decreased Bmax (3.5×) and slightly increased Kd. | Ebisawa et al., 1999 |
| S103A | (2.28) | Human | COS-7 | No change in Bmax or Kd. | Conway et al., 2001 |
| M107T | (3.32) | Human | COS-7 | No change in Bmax or Kd. | Conway et al., 2001; Kokkola et al., 1998 |
| S110Aa | (3.35) | Human | COS-7 | Decreased Bmax (10×), increased Kd (8×) and EC50 of cAMP production (22×). No change in Ki of luzindole | Conway et al., 2001 |
| S114Aa | (3.39) | Human | COS-7 | Decreased Bmax (4×), increased Kd (9×) and EC50 of cAMP production (14×). No change in Ki of luzindole. | Conway et al., 2001 |
| N124A/K | (3.49) | Human | AtT20 | Decreased Bmax (21×), tends to be retained in Golgi. No specific binding. | Nelson et al., 2001 |
| N124A | (3.49) | Human | Saccharomyces cerevisiae | Increased EC50 for melatonin (230×). | Kokkola et al., 1998 |
| N124L | (3.49) | Human | AtT20 | Decreased Bmax (21×), tends to be aggregated near surface. No specific binding. | Nelson et al., 2001 |
| N124D/E | (3.49) | Human | AtT20 | No change in Bmax or Kd. Melatonin induced inhibition of cAMP (efficacy) and voltage-sensitive Ca2+ channels, but not Kir3.1/3.2 potassium channel activation. | Nelson et al., 2001 |
| A157V | (4.55) | Human | COS cells | Heterozygous polymorphism with no phenotype. No change in Bmax or Kd. | Ebisawa et al., 1999 |
| H195Aa | (5.46) | Human | S. cerevisiae | Decreased EC50 (3–6×). N-acetylserotonin gave an apparent saturable response, whereas the wild-type receptor did not saturate at the same concentrations. | Kokkola et al., 1998 |
| H211F/l | (5.46) | Ovine | COS-7 | Increase Kd (6×) with melatonin. Decreased Ki (3–15×) with N-NEA. No change in Ki with N-acetylserotonin. | Conway et al., 1997 |
| V192T + H195A | (5.42 + 5.46) | Human | S. cerevisiae | No specific response | Kokkola et al., 1998 |
| V208A | (5.42) | Ovine | COS-7 | No change in Kd or in Ki of several melatonin analogs. | Conway et al., 1997 |
| V208L | (5.42) | Ovine | COS-7 | Increased Kd and Ki for several melatonin analogs (5–12×). | Conway et al., 1997 |
| A252C | (6.49) | Human | COS-7 | No change in Kd or Bmax. | Conway et al., 2000 |
| Human | COS-7 | No change in Kd or Bmax. | Gubitz and Reppert, 2000 | ||
| G258T | (6.55) | Human | COS-7 | Specific binding drastically reduced | Gubitz and Reppert, 2000; Conway et al., 2000 |
| A252C + G258T | (6.49 + 6.55) | Human | COS-7 | No specific binding | Gubitz and Reppert, 2000 |
| P253A | (6.50) | Human | S. cerevisiae | No specific response. | Kokkola et al., 1998 |
| A202D, H342R, I347V | (ext. loop3, C-terminal) | Ovine | L-cells | Polymorphism of previously cloned ovine MT1. No phenotype in vivo and fully functional in mouse. L cells as shown by high affinity binding, competition binding analysis, GTPγS and inhibition of cAMP. | Barrett et al., 1997 |
| S280A | (7.38) | Human | S. cerevisiae | No change in apparent EC50 | Kokkola et al., 1998 |
| S280F + A284G | (7.38 + 7.42) | Human | S. cerevisiae | No specific response | Kokkola et al., 1998 |
N-NEA, N-[2-(1-naphthyl) ethyl]acetamide.
↵a Amino acid residues important for modulating binding to the MT1 receptor (Farce et al., 2008).