Existence and nature of the chloride pump

Abstract

Seven widely documented mechanisms of chloride transport across plasma membranes are: anion-coupled antiport, sodium symport, sodium-potassium-chloride symport, potassium chloride symport, proton-coupled symport, an electrochemical coupling process and chloride channels. No direct genetic evidence has yet been provided for primary active chloride transport despite numerous reports of cellular Cl(-)- stimulated ATPases coexisting, in the same tissue, with uphill chloride transport that could not be accounted for by the four common chloride transport processes. Cl(-)-stimulated ATPases are a common property of practically all biological cells with the major location being of mitochondrial origin. It also appears that plasma membranes are sites of Cl(-)-stimulated ATPase activity. Recent studies of Cl(-)-stimulated ATPase activity and chloride transport in the same membrane system, including liposomes, suggest a mediation by the ATPase in net movement of chloride up its electrochemical gradient across plasma membranes. Further studies, especially from a molecular biological perspective, are required to confirm a direct transport role to plasma membrane-localized Cl(-)-stimulated ATPases.

Energizing the plasmalemma of marine photosynthetic organisms: the role of primary active transport

“…Similar horizontal gene transfer is required to account for the distribution of P(II)-type H + -ATPases and P(II)-type Na + -ATPases among marine algae with plastids derived from secondary or tertiary endosymbiosis (Chan et al ., 2011, 2012; Burki et al ., 2020). The origin of the F-ATPase that pumps Cl − in some ulvophycean Chlorophyta (Table 3) is unclear; metazoan Cl − -ATPases seem to be P-ATPases (Gerencser & Zhang, 2003).…”

“…As well as variants pumping H + , Na + , K + , Mg 2+ and Ca 2+ (topological type II: Thever & Saier, 2009, in prokaryotes and eukaryotes), there are also P-type ATPases (topological type I, Thever & Saier, 2009, not considered further here) that pump out metal cations such as Cu(I), Ag(I), Zn(II), Cd(II) and Pb(II) (Kuhlbrandt, 2004; Thever & Saier, 2009; Bublitz et al ., 2011; Palmgren & Nissen, 2011; Søndergaard & Pedersen, 2015). There is also an F-type Cl − influx ATPase in the plasmalemma of some marine algae, as well as P-type Cl − -ATPases as found in metazoans (Gerencser & Zhang, 2003; Raven, 2017). There are also ATP (adenosine triphosphate) binding cassette proteins (sometimes referred to as ABC transporters) involved in active solute influx at the plasmalemma, although there is little evidence of these in marine photosynthetic organisms (Chan et al ., 2011, 2012; but see Badger & Price, 2003 for HCO 3 − accumulation in freshwater and marine cyanobacteria).…”

The P-Type ATPase Superfamily

“…The others catalyze uptake and/or efflux of various cations in all domains of life. Evidence for P-type ATPases catalyzing transport of other ions in animals such as chloride has been presented [Gerencser and Zhang, 2003], but the molecular identities of these enzymes have not been achieved.…”

Halorhodopsin pumps Cl–and bacteriorhodopsin pumps protons by a common mechanism that uses conserved electrostatic interactions

“…I ons bind to proteins to carry out many essential biological reactions, including muscle function (1), signal transduction (2), protein-protein interactions (3), and oxygen transport (4). The transmembrane electrochemical gradient generated by ion and proton pumps drives key processes such as ATP synthesis and nerve transmission (5). Proton and ion transfer processes, protein-protein interactions, and enzyme catalysis often rely on charged amino acids (6).…”