XXII. BIOCHEMICKÝ ZJAZD - Jesseniova lekárska fakulta

Posters
57.
BIOCHEMICAL AND MOLECULar ANALYSIS OF NITraTE-RESISTANT
MUTANT OF MethanothermobaCTer thermautotrophICus
Monika Vidová, Zuzana Nováková and Peter Šmigáň
Institute of Animal Biochemistry and Genetics SAV Bratislava
In spite of many studies over the past decade, the processes of energy conservation
in methanoarchaea have not yet been satisfactorily elucidated. To contribute to the
solution of this complex problem, we started with a systematic genetic approach to the
problem of energy conservation in methanoarchaea. This work presents a microbiological,
biochemical and molecular analysis of a spontaneous mutant of Methanothermobacter
thermautotrophicus resistant to nitrate. Nitrate inhibits the A 1
cytoplasmatic domain of
A 1
A 0
-ATP synthase.
Nitrate inhibits methanogenesis in the wild-type cells in the presence of 30 mM nitrate;
however, the nitrate-resistant mutant exhibited two times higher methanogenesis, even
in the presence of 70 mM nitrate. While nitrate profoundly inhibited ATP synthesis driven
by methanogenic electron transport in the wild type, only a slight inhibition was observed
in the mutant strain. These results suggested a modification in the ATP-synthesizing
system of the mutant strain. The sequence of the complete A 1
A 0
-ATP synthase operon
(MTH952 – MTH961) in the wild-type and mutant strains was determined and compared.
Two mutations leading to amino acid substitutions in two A 1
A 0
-ATP synthase subunits
were identified – Ala 337
Val in subunit A and Ala 292
Ser in subunit B. Moreover, this study
revealed the differential expression of several proteins that may contribute to nitrate
resistance. The results imply that changes of nitrate sensitivities of nitrate-resistant
mutant is due to mutational substitutions in the A 1
A 0
-ATP synthase operon.
XXII. Biochemistry Congress, Martin
177