2bsa: Difference between revisions

Ferredoxin-NADP+ reductase (FNR) catalyzes the reduction of NADP+ to NADPH, in an overall reversible reaction, showing some differences in the, mechanisms between cyanobacterial and higher plant FNRs. During hydride, transfer it is proposed that the FNR C-terminal Tyr is displaced by the, nicotinamide. Thus, this C-terminal Tyr might be involved not only in, modulating the flavin redox properties, as already shown, but also in, nicotinamide binding and hydride transfer. FNR variants from the, cyanobacterium Anabaena in which the C-terminal Tyr has been replaced by, Trp, Phe, or Ser have been produced. All FNR variants show enhanced NADP+, and NAD+ binding, especially Tyr303Ser, which correlates with a noticeable, improvement of NADH-dependent reactions. Nevertheless, the Tyr303Ser, variant shows a decrease in the steady-state kcat value with NADPH. Fast, kinetic analysis of the hydride transfer shows that the low efficiency, observed for this mutant FNR under steady-state conditions is not due to a, lack of catalytic ability but rather to the strong enzyme-coenzyme, interaction. Three-dimensional structures for Tyr303Ser and Tyr303Trp, variants and its complexes with NADP+ show significant differences between, plant and cyanobacterial FNRs. Our results suggest that modulation of, coenzyme affinity is highly influenced by the strength of the, C-terminus-FAD interaction and that subtle changes between plant and, cyanobacterial structures are able to modify the energy of that, interaction. Additionally, it is shown that the C-terminal Tyr of FNR, lowers the affinity for NADP+/H to levels compatible with steady-state, turnover during the catalytic cycle, but it is not involved in the hydride, transfer itself.

2BSA is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Anabaena_sp. Anabaena sp.] with FAD and NAP as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Ferredoxin--NADP(+)_reductase Ferredoxin--NADP(+) reductase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.18.1.2 1.18.1.2] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2BSA OCA].  

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