Dr Manuela M. Pereira, Institute of Chemical and Biological Technology, New University of Lisbon, Portugal.
Exploring NADH:quinone Oxidreductases
Almost all catabolic pathways involve direct or indirectly the transfer of electrons to the pyridine nucleotides NAD or NADP . Electrons are then feed to the respiratory chain by NADH dehydrogenases. We have been exploring two different types of NADH:quinone oxidoreductases: respiratory complex I (CpI) and type II or alternative NADH dehydrogenase (NDH-2). We demonstrated the presence of Na /H antiporter activity in CpI, by developing an original approach using 23Na-NMR spectroscopy. We observed that CpIs from R. marinus and E. coli present the antiporter activity, but that from P. denitrificans does not. We hypothesized a correlation between the type of quinone used as substrate and the presence of the antiporter activity. We observed that complex I from E. coli devoid of the NuoL subunit still translocates H , but does not transport Na . These results indicate the involvement of NuoL subunit in Na transport by CpI. Our results on NDH-2 demonstrated unequivocally the functional presence of distinct binding sites for the two substrates, resolving the controversy whether the substrates in NDH-2 bind to the same site. We also showed the establishment of a ternary complex upon turnover and identify quinone reduction as the rate limiting step. This work stimulated us to perform a deep and broad bioinformatic analysis, which allowed systematizing several properties of NDH-2s: (i) the existence of additional sequence motifs with putative regulatory functions, (ii) specificity towards NADH or NADPH and (iii) the type of quinone binding motif. We also explored the catalytic mechanism of NDH-2 by investigating the common elements of all NDH-2s, based on the rationale that conservation of such elements reflects their structural/functional importance. We identified two proton pathways possibly involved in the protonation of the quinone and propose the first catalytic mechanism for NDH-2 family.
ABOUT THE PRESENTER
Manuela M. Pereira is Principal Investigator and head of the group of Biological Energy Transduction at the New University of Lisbon. She has a PhD in Biochemistry and has been dedicated to exploring the molecular mechanisms of key nanomachines, namely those involved in respiration and bioenergetic metabolism. Manuela is author of 70 peer reviewed articles, most as corresponding author. She is a member of the Scientific Advisory Board of the Max Planck Institute for Biophysics and the Executive Committee of the European Biophysics Societies’ Association (2011-15). As President of the Portuguese Biophysical Society (2008-15) she took several initiatives to promote biophysics in Portugal and Portuguese affiliated science abroad. Manuela chaired the European Bioenergetics Conference, EBEC2014.
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