title: Probing a polar cluster in the retinal binding pocket of bacteriorhodopsin by a chemical design approach.
abstract: Bacteriorhodopsin has a polar cluster of amino acids surrounding the retinal molecule, which is responsible for light harvesting to fuel proton pumping. From our previous studies, we have shown that threonine 90 is the pivotal amino acid in this polar cluster, both functionally and structurally. In an attempt to perform a phenotype rescue, we have chemically designed a retinal analogue molecule to compensate the drastic effects of the T90A mutation in bacteriorhodopsin. This analogue substitutes the methyl group at position C(13) of the retinal hydrocarbon chain by and ethyl group (20-methyl retinal). We have analyzed the effect of reconstituting the wild-type and the T90A mutant apoproteins with all-trans-retinal and its 20-methyl derivative (hereafter, 13-ethyl retinal). Biophysical characterization indicates that recovering the steric interaction between the residue 90 and retinal, eases the accommodation of the chromophore, however it is not enough for a complete phenotype rescue. The characterization of these chemically engineered chromoproteins provides further insight into the role of the hydrogen bond network and the steric interactions involving the retinal binding pocket in bacteriorhodopsin and other microbial sensory rhodopsins.
authors.affiliation: Departament de Bioquímica i de Biologia Molecular and Centre d'Estudis en Biofísica, Universitat Autònoma de Barcelona, Barcelona, Spain.
authors.forename: Rosana
authors.initials: R
authors.lastname: Simón-Vázquez
authors.forename: Marta
authors.initials: M
authors.lastname: Domínguez
authors.forename: Víctor A
authors.initials: VA
authors.lastname: Lórenz-Fonfría
authors.forename: Susana
authors.initials: S
authors.lastname: Alvarez
authors.forename: José-Luís
authors.initials: JL
authors.lastname: Bourdelande
authors.forename: Angel R
authors.initials: AR
authors.lastname: de Lera
authors.forename: Esteve
authors.initials: E
authors.lastname: Padrós
authors.forename: Alex
authors.initials: A
authors.lastname: Perálvarez-Marín
mesh_terms: D000221:Adaptation, Ocular; D001224:Aspartic Acid / Q000378:metabolism; D001436:Bacteriorhodopsins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D001671:Biochemistry / Q000379:methods*; D001692:Biological Transport; D019617:Halobacterium salinarum / Q000378:metabolism; D008958:Models, Molecular; D050505:Mutant Proteins / Q000378:metabolism; D011489:Protein Denaturation; D055550:Protein Stability; D012172:Retinaldehyde / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature
chemical_list: D050505:Mutant Proteins; D001224:Aspartic Acid; D001436:Bacteriorhodopsins; D012172:Retinaldehyde