This family is a transmembrane organic solute transport protein. In vertebrates these proteins form a complex with Ostbeta, and function as bile transporters [1]. In plants they may transport brassinosteroid-like compounds and act as regulators of cell death [2].

1: The heteromeric organic solute transporter alpha-beta, Ostalpha-Ostbeta, is an ileal basolateral bile acid transporter. Dawson PA, Hubbert M, Haywood J, Craddock AL, Zerangue N, Christian WV, Ballatori N; J Biol Chem. 2005;280:6960-6968. PMID:15563450

2: Lazarus1, a DUF300 protein, contributes to programmed cell death associated with arabidopsis acd11 and the hypersensitive response. Malinovsky FG, Brodersen P, Fiil BK, McKinney LV, Thorgrimsen S, Beck M, Nielsen HB, Pietra S, Zipfel C, Robatzek S, Petersen M, Hofius D, Mundy J; PLoS One. 2010;5:e12586. PMID:20830211