IBR   13079
INSTITUTO DE BIOLOGIA MOLECULAR Y CELULAR DE ROSARIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
The role of C-terminus in the catalytic mechanism of a bacterial ferredoxin-NADP+ reductase
Autor/es:
ANA BORTOLOTTI; NÉSTOR CARRILLO; NÉSTOR CORTEZ
Lugar:
Carlos Paz (Argentina)
Reunión:
Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2008
Resumen:
Ferredoxin-NADP+ reductases (FPRs) are flavoenzymes that catalyze reversible reactions between obligatory one-electron carriers and two-electron donors/acceptors. Structural analysis of reductases from different sources revealed that these flavoproteins are made up of two domains that bind the FAD and NADP(H) molecules, and helped to identify structural features that account for the difference in catalytic competence. Enzymes found in photosynthetic organisms are characterized by an extended FAD conformation and an invariant tyrosine residue at the C-terminus, responsible for high catalytic efficiency. Instead, the enzyme from eubacteria bind FAD in a bent conformation and the amino acid facing the flavin may be aromatic or aliphatic. In the Rhodobacter capsulatus reductase, the binding of NADP(H) leads the displacement of the C-terminal tail of the protein to accommodate the nicotinamide ring for hydride transfer. We evaluate the role of the terminal residues A267 to I272 on the coenzyme binding and the catalytic activity. FAD was stably bound to all studied mutants after uv-visible spectroscopy. A six fold decrease of activity resulted from the A266Y mutation, but a still higher fall of catalytic rates corresponded to the A266YΔ and A266Δ mutants. Our results evidence the contribution of the C-terminus structure to the catalytic mechanism in bacterial ferredoxin-NADP+ reductases.