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 SchemeTM No.SpeciesExpression SystemCharacterizationReference
R54W(1.59)HumanCOS cellsHeterozygous polymorphism with no phenotype. Decreased Bmax (3.5×) and slightly increased Kd.Ebisawa et al., 1999
S103A(2.28)HumanCOS-7No change in Bmax or Kd.Conway et al., 2001
M107T(3.32)HumanCOS-7No change in Bmax or Kd.Conway et al., 2001; Kokkola et al., 1998
S110Aa(3.35)HumanCOS-7Decreased Bmax (10×), increased Kd (8×) and EC50 of cAMP production (22×). No change in Ki of luzindoleConway et al., 2001
S114Aa(3.39)HumanCOS-7Decreased 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)HumanAtT20Decreased Bmax (21×), tends to be retained in Golgi. No specific binding.Nelson et al., 2001
N124A(3.49)HumanSaccharomyces cerevisiaeIncreased EC50 for melatonin (230×).Kokkola et al., 1998
N124L(3.49)HumanAtT20Decreased Bmax (21×), tends to be aggregated near surface. No specific binding.Nelson et al., 2001
N124D/E(3.49)HumanAtT20No 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)HumanCOS cellsHeterozygous polymorphism with no phenotype. No change in Bmax or Kd.Ebisawa et al., 1999
H195Aa(5.46)HumanS. cerevisiaeDecreased 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)OvineCOS-7Increase 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)HumanS. cerevisiaeNo specific responseKokkola et al., 1998
V208A(5.42)OvineCOS-7No change in Kd or in Ki of several melatonin analogs.Conway et al., 1997
V208L(5.42)OvineCOS-7Increased Kd and Ki for several melatonin analogs (5–12×).Conway et al., 1997
A252C(6.49)HumanCOS-7No change in Kd or Bmax.Conway et al., 2000
HumanCOS-7No change in Kd or Bmax.Gubitz and Reppert, 2000
G258T(6.55)HumanCOS-7Specific binding drastically reducedGubitz and Reppert, 2000; Conway et al., 2000
A252C + G258T(6.49 + 6.55)HumanCOS-7No specific bindingGubitz and Reppert, 2000
P253A(6.50)HumanS. cerevisiaeNo specific response.Kokkola et al., 1998
A202D, H342R, I347V(ext. loop3, C-terminal)OvineL-cellsPolymorphism 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)HumanS. cerevisiaeNo change in apparent EC50Kokkola et al., 1998
S280F + A284G(7.38 + 7.42)HumanS. cerevisiaeNo specific responseKokkola 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).