sodium bicarbonate cotransporter 3 (sodium bicarbonate cotransporter 2, sodium bicarbonate cotransporter 2b, bicarbonate transporter, solute carrier family 4 member 7, SLC4A7, BT, NBC2, NBC2B, NBC3, SBC2, SLC4A6)

Function

• electroneutral Na+ & HCO3- dependent cotransporter with a Na+:HCO3- 1:1 stoichiometry
• regulates intracellular pH
• bicarbonate salvage in secretory epithelia (putative)
• Na+ channel activity (putative)
• transporter activity is regulated by carbonic anhydrase 2, cAMP & PKA; insensitive to stilbene
• interacts with CFTR through SLC9A3R1/EBP50
• interacts with USH1C
• forms a complex with ATP6V1B1 & SLC9A3R1/EBP50
• PDZ-binding motif mediates interaction with the CFTR, SLC9A3R1/EBP50 complex & USH1C
• interacts with CA2/carbonic anhydrase 2 (pH dependent)

Kinetic parameters:

• KM=24 mM for external Na+

Compartment

• cell membrane, basolateral cell membrane,
• apical cell membrane ?
• localizes to the stereocilia of cochlear outer hair cells & to lateral membrane of cochlear inner hair cells

Alternative splicing

named isoforms=5

Expression

• highly expressed in testis, spleen
• expressed in retina, colon, small intestine, ovary, thymus, prostate, muscle, heart, kidney
• isoform 1 is expressed in skeletal muscle, heart muscle

More general terms

• glycoprotein
• transmembrane 11e protein
• phosphoprotein
• solute carrier family 4 (SLC4, SLC4A)

Database

• OMIM: https://mirror.omim.org/entry/603353
• UniProt: http://www.uniprot.org/uniprot/Q9Y6M7.html