Effect of n-octanesulphonylacetamide (OSA) on ATP and protein expression in Mycobacterium bovis BCG.
OBJECTIVE
To determine the effect on BCG of n-octanesulphonylacetamide (OSA), a novel compound of the class beta-sulphonylcarboxamides, which has potent in vitro activity against pathogenic mycobacteria.


RESULTS
The effect of OSA in BCG was examined using two-dimensional protein electrophoresis. Treatment of BCG with OSA resulted in overexpression of two proteins identified as the b-subunit of ATP synthase (Rv1306) and a 17 kDa heat shock protein (Rv0251c). [35S]Methionine pulse-labelling revealed that overexpression occurred within as little as 3.5 h post-exposure. These results were confirmed by RT-PCR. ATP levels decreased in OSA-treated BCG at 5 min, and 1, 3 and 24 h, with a 64%, 45%, 54% and 73% reduction in ATP, respectively. Only dicyclohexylcarbodiimide (DCCD), a known ATP synthase inhibitor, had a similar effect. No appreciable difference in ATP level was observed in BCG treated with standard antimycobacterial drugs, additional respiratory chain inhibitors or a fatty acid synthase inhibitor at a comparable time-point. Protein synthesis decreased within 5 min of exposure to OSA (56%), DCCD (74%) and thenoyltrifluoroacetone (TTFA) (77%). Ethanol (2.3%) potentiated the activity of OSA. In contrast, no synergic effect was observed with streptomycin and ethanol. Mycolic acid levels decreased 79% with DCCD, 46% with TTFA, a complex II inhibitor, and 43% with OSA compared with untreated controls.


CONCLUSIONS
Our results suggest that OSA may interfere directly or indirectly with ATP synthase and possibly other components of the mycobacterial respiratory chain. These effects may hinder energy production, leading to interruption in the synthesis of large macromolecules including proteins and mycolic acids.
Parrish
Nicole M
NM
Department of Pathology, School of Medicine, Johns Hopkins University, Baltimore, MD, USA.
Ko
Chiew G
CG
Hughes
Minerva A
MA
Townsend
Craig A
CA
Dick
James D
JD
D000081:Acetamides / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D000476:Alkanesulfonates / Q000494:pharmacology*; D000995:Antitubercular Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000096:biosynthesis*; D025243:Bacterial Proton-Translocating ATPases / Q000096:biosynthesis; D004579:Electron Transport / Q000187:drug effects; D015180:Electrophoresis, Gel, Two-Dimensional; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006360:Heat-Shock Proteins / Q000096:biosynthesis; D009163:Mycobacterium bovis / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D009171:Mycolic Acids / Q000378:metabolism; D021122:Protein Subunits
D000081:Acetamides; D000476:Alkanesulfonates; D000995:Antitubercular Agents; D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D006360:Heat-Shock Proteins; D009171:Mycolic Acids; C434282:N-octanesulfonylacetamide; D021122:Protein Subunits; D000255:Adenosine Triphosphate; D025243:Bacterial Proton-Translocating ATPases