Bacterial Na+ - or H+ -coupled ATP synthases operating at low electrochemical potential.

摘要: In certain strictly anaerobic bacteria, the energy for growth is derived entirely from a decarboxylation reaction. A prominent example Propionigenium modestum, which converts free of (S)-methylmalonyl-CoA to propionyl-CoA (DeltaG degrees =-20.6 kJ/mol) into an electrochemical Na(+) ion gradient across membrane. This source used as driving force ATP synthesis by Na(+)-translocating F(1)F(0) synthase. According bioenergetic considerations, approximately four events are necessary support one ATP. unique feature using instead H(+) coupling has made this synthase paradigm study pathway membrane and its relationship rotational catalysis. The potential (Deltapsi) key convert translocation through F(0) motor components torque. resulting rotation elicits conformational changes at catalytic sites peripheral F(1) domain instrumental synthesis. Alkaliphilic bacteria also face challenge synthesizing low potential, but different reasons. Here, not result insufficient input substrate degradation, inverse pH gradient. consequence high environmental where these grow necessity keep intracellular in neutral range. spite unfavorable condition, alkaliphilic coupled proton motive (DeltamuH(+)) much higher sodium (DeltamuNa(+)). peculiar synthases alkaliphiles specific inhibition their hydrolysis activity. appears be essential strategy survival external pH: if enzyme were operate ATPase, protons would pumped outwards counteract DeltamuH(+), thus wasting valuable compromising acidification cytoplasm alkaline pH.