ATP-dependent low-affinity peptide transporter which translocates a broad spectrum of peptides from the cytosol to the lysosomal lumen for degradation (PubMed:15863492, PubMed:17977821, PubMed:18434309, PubMed:22641697, PubMed:25646430, PubMed:30877195, PubMed:31417173, PubMed:30353140). Displays a broad peptide length specificity from 6-mer up to at least 59-mer peptides with an optimum of 23-mers (PubMed:15863492, PubMed:25646430). Binds and transports smaller and larger peptides with the same affinity (PubMed:31417173). Favors positively charged, aromatic or hydrophobic residues in the N- and C-terminal positions whereas negatively charged residues as well as asparagine and methionine are not favored (PubMed:15863492, PubMed:17977821, PubMed:18434309). a [oligopeptide](in) + ATP + H2O = a [oligopeptide](out) + ADP + H(+) + phosphate Transport activity is limited by threshold levels of luminal peptide (PubMed:25646430). ATP hydrolysis is reduced in the presence of the spatial challenging 18-mer peptide by 50% and the branched 16-mer peptide by 75% (PubMed:31417173). Transport rate of the longer peptides is strongly reduced (PubMed:31417173). Optimum pH is 7.0. Optimum temperature is 37 degrees Celsius. Homodimer (PubMed:15863492, PubMed:30353140). Interacts (via TMD0 region) with LAMP1; this interaction strongly stabilizes ABCB9 and protects ABCB9 against lysosomal degradation (PubMed:22641697). Interacts (via TMD0 region) with LAMP2 (isoform LAMP-2B) (PubMed:22641697). Interacts (via TMD0) with YIF1B; this interaction allows (but is not essential) the ER-to-Golgi trafficking and strongly depends on a salt bridge within TMD0 (PubMed:30877195). May be located in membrane rafts. Takes an intracellular route from the endoplasmic reticulum (ER), via Golgi and early endosomes to late endosomal and lysosomal compartments (PubMed:30877195). Highly expressed in testis, and at moderate levels in brain, spinal cord, and thyroid. Not expressed in monocytes but strongly expressed during differentiation of monocytes to dendritic cells and macrophages. Not induced by interferon-gamma. Divided into an N-terminal domain (TMD0) comprising four transmembrane helices and the following core domain (coreABCB9) (PubMed:18952056). TMD0 is required for lysosomal localization and LAMP1, LAMP2 and YIF1B interaction (PubMed:15577206, PubMed:18175933, PubMed:20377823, PubMed:22641697, PubMed:30877195). The core domain is required for homodimerization and peptide transport activity (PubMed:18952056, PubMed:20377823). Belongs to the ABC transporter superfamily. ABCB family. MHC peptide exporter (TC 3.A.1.209) subfamily. Has also been detected in the endoplasmic reticulum but appears to be a lysosomal protein in vivo. Extended N-terminus. Extended N-terminus. Database for mutations in ABC proteins