Pre-steady-state kinetics and solvent isotope effects support the "billiard-type" transport mechanism in Na⁺ -translocating pyrophosphatase.

ABSTRACT: Membrane-bound pyrophosphatase (mPPase) found in microbes and plants is a membrane H⁺ pump that transports the H⁺ ion generated in coupled pyrophosphate hydrolysis out of the cytoplasm. Certain bacterial and archaeal mPPases can in parallel transport Na⁺ via a hypothetical "billiard-type" mechanism, also involving the hydrolysis-generated proton. Here, we present the functional evidence supporting this coupling mechanism. Rapid-quench and pulse-chase measurements with [³² P]pyrophosphate indicated that the chemical step (pyrophosphate hydrolysis) is rate-limiting in mPPase catalysis and is preceded by a fast isomerization of the enzyme-substrate complex. Na⁺ , whose binding is a prerequisite for the hydrolysis step, is not required for

SUBMITTER: Malinen AM 

PROVIDER: S-EPMC9405524 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature