Involved in pH regulation to eliminate acids generated by active metabolism or to counter adverse environmental conditions. Major proton extruding system driven by the inward sodium ion chemical gradient. Plays an important role in signal transduction. Oligomer (PubMed:21543739). Interacts with CALM1 in a calcium-dependent manner (By similarity). Interacts with TESC (PubMed:18321853). Interacts (via residues 504-563; the juxtamembrane region of the cytoplasmic C-terminal domain) with CHP1 (PubMed:12576672). The interaction with CHP1 occurs at the plasma membrane in a calcium-dependent manner (By similarity). Interacts with CHP2 (PubMed:12576672). The interaction with CHP2 occurs in a calcium-dependent manner (By similarity). Colocalizes with and CHP2 at the plasma membrane (By similarity). Colocalizes with CHP1 at the reticulum endoplasmic and plasma membrane. Not tissue specific. N-glycosylated and O-glycosylated in the N-terminal region. Ubiquitinated, leading to its degradation by the proteasome. Ubiquitination is reduced by CHP1. Belongs to the monovalent cation:proton antiporter 1 (CPA1) transporter (TC 2.A.36) family. The region between transmembrane regions M4 and M5 and between M6 and M7 (also termed intracellular loops IL2 and IL4, respectively) seem to be localized at least in part in the membrane. The hydrophobic region H10 is proposed to be located within the membrane. Although PubMed:18321853 show that TESC-binding results in the maturation and accumulation of SLC9A1 at the cell surface, previous studies with human SLC9A1 report that TESC-binding results in a decrease in activity. The interacting region with TESC is conflicting: It has been reported that SLC9A1 interacts with TESC via the juxtamembrane region of the cytoplasmic C-terminal domain, including residues 505-571 (PubMed:18321853). However, studies with human SLC9A1 report the interaction with TESC via residues 503-545 or via residues 633-815.