P-Chloromercurobenzene sulfonate inhibition of active Cl- transport in plasma membrane vesicles from Aplysia gut

Abstract

Both a Cl(+)-stimulated adenosinetriphosphatase (ATPase) activity and an ATP-dependent Cl- transport process were found in Aplysia foregut absorptive cell plasma membranes. In an attempt to further characterize this transport process, plasma membrane vesicles from Aplysia foregut absorptive cells were prepared utilizing differential centrifugation and sucrose density-gradient techniques. Sulfhydryl ligand participation in ATP-dependent Cl- transport was confirmed in three ways. First, 1,4-dithiothreitol partially restored a p-chloromercurobenzene sulfonate (PCMBS)-inhibited ATP-dependent Cl- transport. Second, 1,4-dithiothreitol restored intravesicular negativity inhibited by PCMBS. Third, 1,4-dithiothreitol had no effect on either ATP-dependent Cl- transport or ATP-dependent intravesicular negativity inhibited by N-ethylmaleimide. These results are consistent with the hypothesis that surface sulfhydryl groups participate in the functioning of the active electrogenic Cl- transport mechanism in Aplysia gut.