La molibdoenzima ARC en Chalmydomonas reinhardtii: Destoxificación y producción de NO

Abstract

The ARC (amidoxime reducing component) protein was discovered in 2006 as a new molybdenum cofactor (Moco)-containing enzyme involved in the reduction of N-hydroxylated compounds (NHC). Proteins of this family are distributed throughout the three kingdoms of living organisms. In this thesis we have identified the ARC protein of Chlamydomonas, and the proteins that interact with it. The role of the ARC protein in regulating the metabolic pathway of nitrate assimilation is proposed, the confirmation of a prediction of its structure, and finally its capacity to store Moco have been addressed. Chapter I The ARC protein is a new molybdoenzyme about which not much is known. This protein is 329 amino acids long with two conserved domains such as the β-barrel and the MOSC. This protein seems to have a role in detoxifying of N-hydroxy compounds such as hydroxylamine purine (HAP), which is a compound analogous to adenine and therefore mutagenic. In this thesis, we have identified this ARC protein in Chlamydomonas as a molybdoenzyme. Chlamydomonas mutants affected in this protein are unable to develop the detoxification activity of HAP, which seems to depend on Moco. Two other proteins responsible for the transfer of electrons from NADH to ARC were also identified. In bacteria this transfer occurs by a ferredoxin domain and a reductase protein (CYSJ), whereas in humans by Cytb5 and Cytb5-R. In Chlamydomonas, we have studied in vivo this capability of transfer for the six ferredoxins and five Cytb5 from the alga, and...