Organic solute transporter subunit beta (IPR029387)

Short name: OSTbeta

Overlapping homologous superfamilies


Family relationships



Organic solute transporter subunit beta (OSTbeta, also known as SLC51B) is an essential component of the Ost-alpha/Ost-beta complex, a heterodimer that acts as the intestinal basolateral transporter responsible for bile acid export from enterocytes into portal blood [PMID: 16317684].

OSTbeta is a single-TM domain polypeptide that forms a transporter complex with Ost-alpha protein, which is a 7-transmembrane (TM) domain containing protein. This heterodimerisation is required for the delivery of the complex to the plasma membrane. The OSTalpha-OSTbeta complex serves as a multispecific transporter that may participate in cellular uptake of bile acids, some endogenous and exogenous steroids, and eicosanoids. It functions via a facilitated diffusion mechanism. Interestingly, this transporter also transports dehydroepiandrosterone sulfate (DHEAS) and pregnenolone sulfate (PREGS), which are major excitatory neurosteroids. This suggests a possible function for OSTalpha-OSTbeta complex in the brain [PMID: 23506901].

GO terms

Biological Process

GO:0015721 bile acid and bile salt transport

Molecular Function

GO:0046982 protein heterodimerization activity
GO:0005215 transporter activity

Cellular Component

GO:0005886 plasma membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.