In silico mutagenesis: a case study of the melanocortin 4 receptor.
The melanocortin 4 receptor (MC4R) is a G-protein-coupled receptor (GPCR) and a key molecule in the regulation of energy homeostasis. At least 159 substitutions in the coding region of human MC4R (hMC4R) have been described experimentally; over 80 of those occur naturally, and many have been implicated in obesity. However, assessment of the presumably functionally essential residues remains incomplete. Here we have performed a complete in silico mutagenesis analysis to assess the functional essentiality of all possible nonnative point mutants in the entire hMC4R protein (332 residues). We applied SNAP, which is a method for quantifying functional consequences of single amino acid (AA) substitutions, to calculate the effects of all possible substitutions at each position in the hMC4R AA sequence. We compiled a mutability score that reflects the degree to which a particular residue is likely to be functionally important. We performed the same experiment for a paralogue human melanocortin receptor (hMC1R) and a mouse orthologue (mMC4R) in order to compare computational evaluations of highly related sequences. Three results are most salient: 1) our predictions largely agree with the available experimental annotations; 2) this analysis identified several AAs that are likely to be functionally critical, but have not yet been studied experimentally; and 3) the differential analysis of the receptors implicates a number of residues as specifically important to MC4Rs vs. other GPCRs, such as hMC1R.
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York, USA. bromberg@rostlab.org
Yana
Y
Bromberg
John
J
Overton
Christian
C
Vaisse
Rudolph L
RL
Leibel
Burkhard
B
Rost
D000595:Amino Acid Sequence; D000818:Animals; D003198:Computer Simulation; D006801:Humans; D051379:Mice; D016296:Mutagenesis; D017354:Point Mutation; D044105:Receptor, Melanocortin, Type 4 / Q000235:genetics*; D043562:Receptors, G-Protein-Coupled
C470072:MC4R protein, human; D044105:Receptor, Melanocortin, Type 4; D043562:Receptors, G-Protein-Coupled