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Título

ThnA3 and ThnY, electron transfer proteins of the dioxygenase systems, evolved to become regulators of the tetralin biodegradation operons

AutorLedesma García, Laura ; Reyes-Ramírez, Francisca ; Santero, Eduardo
Fecha de publicación2013
CitaciónXXXVI Congreso de la SEBBM (2013)
ResumenRegulation of the tetralin biodegradation genes (thn) in Sphingomonas macrogolitabida strain TFA is complex and requires the action of two regulatory proteins, named ThnR and ThnY. ThnR is a LysR-type transcriptional regulator, while ThnY exhibits similarity to NAD(P)H-dependent ferredoxin reductases of the dioxygenase systems involved in the degradation of aromatic compounds. In spite of its amino acid sequence, ThnY has a regulatory role controlling the activity of ThnR. ThnA3, is a Rieske-type ferredoxin that in addition to delivering electrons to the tetralin dioxygenase prevents gratuitous induction of the thn genes by inducer molecules that are not substrates of the catabolic pathway. How the discriminatory function of ThnA3 is transmitted to the regulatory system, ThnR-ThnY, is of critical importance. We have generated some amino acid substitutions within ThnY that provoke a complete loss of the discrimination capacity of the thn system, which provide genetic evidences that ThnA3 exerts its negative modulation via the regulator ThnY. This conclusion is further supported by the in vitro analysis showed here: (i) isothermal titration calorimetry and (ii) stopped-flow assays, which demonstrate that ThnA3 and ThnY form a binary complex in solution and that ThnA3 is able to reduce ThnY. The proposed mechanism for thn regulation implies that in the absence of a suitable substrate of the dioxygenase enzyme, ThnA3 accumulated in its reduced form interacts with and reduces ThnY, thus preventing transcriptional activation in response to a potential inducer that is not a substrate of the catabolic pathway.
DescripciónResumen del póster presentado al XXXVI Congreso de la Sociedad Española de Bioquímica y Biología Molecular celebrado en Madrid del 3 al 6 de septiembre de 2013.-- et al.
URIhttp://hdl.handle.net/10261/130224
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