The alpha and omega of G-protein coupled receptors: a novel method for classification. Part 2. Bin classification

A novel way of classification of G-protein coupled receptors is presented that is only based on receptor sequence information by counting of amino acid residues. It involves the number of amino acid residues between the Asn residue in TM1 and the residue Cys in the loop between TM4 and TM5, the number of residues between the latter Cys residue and Pro residue in TM6, and the number of residues between the latter Pro and the last amino acid residue (called omega) in the sequence. The classification of 131 sequences, covering biogenic amine, opioid and somatostatin receptors, is visualized by means of a diagram which is referred to as a bin map. Each bin in the diagram encloses all the sequences that belong to one and only one receptor type or subtype. This so-called bin classification was obtained by means of the genetic algorithm methodology, which offers new opportunities for classifying proteins.