Two hypotheses--one answer. Sequence comparison does not support an evolutionary link between halobacterial retinal proteins including bacteriorhodopsin and eukaryotic G-protein-coupled receptors.
The structure of bacteriorhodopsin (BR) of Halobacterium halobium is known. Despite the lack of sequence similarities it is often taken as a model for eukaryotic G-protein-coupled receptors (GPCRs). Recently two hypotheses were used to support the homology of BR and GPCRs, namely evolution by exon shuffling and evolution by gene duplication. BR is a member of a family of halobacterial retinal proteins. The sequences of eight members of this family were used to test the two hypotheses. Based on sequence comparison, no indication for an evolutionary linkage between the two protein families could be found.
Soppa
J
J
Max-Planck-Institut für Biochemie, Martinsried, Germany.
D000595:Amino Acid Sequence; D000818:Animals; D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000235:genetics; D005075:Biological Evolution; D005091:Exons; D019204:GTP-Binding Proteins; D019617:Halobacterium salinarum / Q000737:chemistry* / Q000235:genetics; D025602:Halorhodopsins; D006801:Humans; D008969:Molecular Sequence Data; D005810:Multigene Family; D017433:Protein Structure, Secondary; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000235:genetics; D016415:Sequence Alignment
D025602:Halorhodopsins; D011956:Receptors, Cell Surface; D001436:Bacteriorhodopsins; D019204:GTP-Binding Proteins