The Molecular Basis for the Natural Resistance of the Cytochrome bc1 Complex from Strobilurin-Producing Basidiomycetes to Center QP Inhibitors

Authors


  • Note. The nove nucleotide sequence data published here have been submitted to the GenBankTM/EMBL Data Bank and are available under accession numbers X88000 (S. tenacellus), X87997 (M. galopoda), X87998 (M. viridimarginata).

U. Brandt, Universitätsklinkum Frankfurt, Zentrum der Biologischen Chemie, Theodor-Stern-Kai 7, Haus 25B, D-60590 Frankfurt am Main, Germany
Fax: +49 69 6301 6970.

Abstract

Mitochondria from the strobilurin A producing basidiomycetes Strobilurus tenacellus and Mycena galopoda exhibit natural resistance to (E)-β-methoxyacrylate inhibitors of the ubiquinol oxidation center (center Qp) of the cytochrome bc1 complex. Isolated cytochrome bc1 complex from S. tenacellus was found to be highly similar to that of Saccharomyces cerevisiae with respect to subunit composition, as well as spectral characteristics and midpoint potentials of the heme centers.

To understand the molecular basis of natural resistance, we determined the exon/intron organization and deduced the sequences of cytochromes b from S. tenacellus, M. galopoda and a third basidiomycete, Mycena viridimarginata, which produces no strobilurin A. Comparative sequence analysis of two regions of cytochrome b known to contribute to the formation of center Qp suggested that the generally lower sensitivity of all three basidiomycetes was due to the replacement of a small amino acid residue in position 127 by isoleucine. For M. galopoda replacement of Gly143 by alanine and Gly153 by serine, for S. tenacellus replacement of a small residue in position 254 by glutamine and Asn261 by aspartate was found to be the likely causes for resistance to (E)-β-methoxyacrylates. The latler exchange is also found in Schizosaccharomyces pombe, which we found also to be naturally resistant to (E)-β-methoxyacrylates.

Abbreviations
Center Qp and center QN

ubiquinol oxidation (Qo) center and ubiquinone reduction (Qi) center of cytochrome bc1 Complex

I50

mol inhibitor required/mol cytochrome bc1 complex to inhibit mitochondrial respiration by 50%

NQNO

2n-nonyl-4-hydroxy-quinoline-N -oxide

PhMeSO2F

phenylmethylsulfonyl fluoride

RT-PCR

reverse transcriptase-polymerase chain reaction

UHNQ

3n-undecyl-2-hydroxy-1,4-naphthocpinone

ORF

open reading frame

Enzyme
 

Ubihydroquinone:ferriceytochrome-c oxidoreductase (EC 1.10.2.2)

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