Enables L-glutamine transmembrane transporter activity and L-histidine transmembrane transporter activity. Acts upstream of or within amino acid transport; cellular response to potassium ion starvation; and positive regulation of transcription from RNA polymerase II promoter in response to acidic pH. Located in apical plasma membrane. Is integral component of plasma membrane. Is expressed in several structures, including central nervous system; metanephros; pancreas; pericardium; and retina. Orthologous to human SLC38A3 (solute carrier family 38 member 3). [provided by Alliance of Genome Resources, Apr 2022]