Affiliation:
1. Dipartimento di Biologia Cellulare e dello Sviluppo, Università di Roma “La Sapienza,” 00185 Rome
2. Dipartimento di Genetica, Antropologia e Evoluzione, Università degli Studi di Parma, 43100 Parma, Italy
Abstract
ABSTRACT
We have isolated a
Kluyveromyces lactis
mutant unable to grow on all respiratory carbon sources with the exception of lactate. Functional complementation of this mutant led to the isolation of
KlSDH1
, the gene encoding the flavoprotein subunit of the succinate dehydrogenase (SDH) complex, which is essential for the aerobic utilization of carbon sources. Despite the high sequence conservation of the
SDH
genes in
Saccharomyces cerevisiae
and
K. lactis
, they do not have the same relevance in the metabolism of the two yeasts. In fact, unlike
SDH1
,
KlSDH1
was highly expressed under both fermentative and nonfermentative conditions. In addition to this, but in contrast with
S. cerevisiae
,
K. lactis
strains lacking
KlSDH1
were still able to grow in the presence of lactate. In these mutants, oxygen consumption was one-eighth that of the wild type in the presence of lactate and was normal with glucose and ethanol, indicating that the respiratory chain was fully functional. Northern analysis suggested that alternative pathway(s), which involves pyruvate decarboxylase and the glyoxylate cycle, could overcome the absence of SDH and allow (i) lactate utilization and (ii) the accumulation of succinate instead of ethanol during growth on glucose.
Publisher
American Society for Microbiology
Subject
Molecular Biology,General Medicine,Microbiology
Cited by
20 articles.
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