Browsing by Author "Canessa, P."

Now showing 1 - 4 of 4
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    Circadian clocks and the regulation of virulence in fungi : getting up to speed
    (2016) Hevia, M.; Canessa, P.; Larrondo Castro, Luis Fernando
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    Cloning and characterization of the genes encoding the high-affinity iron-uptake protein complex Fet3/Ftr1 in the basidiomycete Phanerochaete chrysosporium
    (2007) Larrondo Castro, Luis Fernando; Canessa, P.; Melo Ledermann, Francisco Javier; Polanco, R.; Vicuña, Rafael
    MCO1, a multicopper oxidase from Phanerochaete chrysosporium exhibiting strong ferroxidase activity, has recently been described. This enzyme shows biochemical and structural similarities with the yeast Fet3p, a type I membrane glycoprotein that efficiently oxidizes Fe(II) to Fe(III) for its subsequent transport to the intracellular compartment by the iron permease Ftr1p. The genome database of P. chrysosporium was searched to verify whether it includes a canonical fet3 in addition to mco1, and single copies of fet3 and ftr1 orthologues were found, separated by a divergent promoter. Pc-fet3 encodes a 628 aa protein that exhibits overall identities of about 40 % with other reported Fet3 proteins. In addition to a secretion signal, it has a C-terminal transmembrane domain, characteristic of these cell-surface-attached ferroxidases. Structural modelling of Pc-Fet3 revealed that the active site has all the residues known to be essential for ferroxidase activity. Pc-ftr1 encodes a 393 aa protein that shows about 38 % identity with several Ftr1 proteins from ascomycetes. Northern hybridization studies showed that the mRNA levels of both genes are reduced upon supplementation of the growth medium with iron, supporting the functional coupling of Fet3 and Ftr1 proteins in vivo.
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    Differential regulation of genes encoding manganese peroxidase (MnP) in the basidiomycete Ceriporiopsis subvermispora
    (2003) Manubens, A.; Avila, M.; Canessa, P.; Vicuña, R.
    We previously identified and characterized three mnp genes coding for manganese peroxidase (MnP) in the white rot fungus Ceriporiopsis subvermispora. In this work, we assessed transcript levels of mnp genes in liquid cultures of this fungus grown under various conditions. In the absence of Mn2+, mnp1 and mnp2 mRNA were detected by Northern hybridization, irrespective of the lack of extracellular MnP activity. Addition of Mn2+ to the cultures led to a marked increase in both transcripts, the highest titers being observed at 10 muM Mn2+ mnp1 mRNA was not detected at Mn2+ concentrations above 80 muM, whereas mnp2 mRNA was still observed at 320 muM Mn2+. Differential regulation of these genes was confirmed by the addition of Cu2+, Zn2+, Ag+ and Cd2+. These metal ions dramatically elevated both transcripts and also allowed the detection of the mnp3 transcript. In most cases, the increase in mRNA levels was partially abolished by the simultaneous presence of Mn2+, although the latter was strictly required to detect extracellular MnP activity. However, the lignin-related compound syringic acid specifically increased the mnp1 transcript, although only in the absence of Mn2+. These results indicate that there is no clear correlation between mnp mRNA levels and MnP activity. In addition, they strongly suggest that Mn2+ plays a post-transcriptional role which is essential for the presence of active MnP in the extracellular fluid.