SLC6A19 is a transmembrane protein that actively transports most neutral amino acids across the apical membrane. Mutations result in Hartnup disorder. 

Antibody validation
This commercial rabbit antibody from Atlas Antibodies (HPA043207) is a polyclonal affinity isolated antibody raised agasint the sequence MVRLVLPNPGLDARIPSLAELETIEQEEASSRPKWDNK. Enhanced validation by the manufacturer was by comparison of IHC stains to RNASeq data. Our validation included staining of formalin-fixed, paraffin-embedded human duodenum, where SLC6A19 is detected within the apical brush border of villous, but not crypt, epithelial cells (right, upper image). In contrast, expression is not detected in the colon (right, lower image), as expected.