The crossing of two unwound transmembrane regions that is the hallmark of the NhaA structural fold is critical for antiporter activity.

Cell pH and Na homeostasis requires Na/H antiporters. The crystal structure of NhaA, the main Escherichia coli Na/H antiporter, revealed a unique NhaA structural fold shared by prokaryotic and eukaryotic membrane proteins. Out of the 12 NhaA transmembrane segments (TMs), TMs III-V and X-XII are topologically inverted repeats with unwound TMs IV and XI forming the X shape characterizing the NhaA fold.

Towards Molecular Understanding of the pH Dependence Characterizing NhaA of Which Structural Fold is Shared by Other Transporters.

Na/H antiporters comprise a super-family (CPA) of membrane proteins that are found in all kingdoms of life and are essential in cellular homeostasis of pH, Na and volume. Their activity is strictly dependent on pH, a property that underpins their role in pH homeostasis. While several human homologues have long been drug targets, NhaA of Escherichia coli has become the paradigm for this class of secondary active transporters as NhaA crystal structure provided insight into the architecture of this molecular machine.

Insight into the direct interaction of Na with NhaA and mechanistic implications.

Na/H antiporters comprise a family of membrane proteins evolutionarily conserved in all kingdoms of life that are essential in cellular ion homeostasis. While several human homologues have long been drug targets, NhaA of Escherichia coli has become the paradigm for this class of secondary active transporters as NhaA crystals provided insight in the structure of this molecular machine. However, structural data revealing the composition of the binding site for Na (or its surrogate Li) is missing, representing a bottleneck in our understanding of the correlation between the structure and function of NhaA.

An angular motion of a conserved four-helix bundle facilitates alternating access transport in the TtNapA and EcNhaA transporters.

There is ongoing debate regarding the mechanism through which cation/proton antiporters (CPAs), like NapA (TtNapA) and Escherichia coli NapA (EcNhaA), alternate between their outward- and inward-facing conformations in the membrane. CPAs comprise two domains, and it is unclear whether the transition is driven by their rocking-bundle or elevator motion with respect to each other. Here we address this question using metadynamics simulations of TtNapA, where we bias conformational sampling along two axes characterizing the two proposed mechanisms: angular and translational motions, respectively.

Cardiolipin is an Optimal Phospholipid for the Assembly, Stability, and Proper Functionality of the Dimeric Form of NhaA Na/H Antiporter.

Cardiolipin (CL) was shown to bound to the dimer interface of NhaA Na/H antiporter. Here, we explore the cardiolipin-NhaA interaction both in vitro and in vivo. Using a novel and straightforward in-vitro assay in which n-dodecyl β-D maltoside (DDM) detergent is used to delipidate the dimer interface and to split the dimers into monomers; the monomers are subsequently exposed to cardiolipin or the other E.