Adaptins are important subunits of heterotetrameric complexes called adaptors, which participate in the clathrin-coated, vesicle-mediated endocytosis and intracellular receptor transport. The gene family of adaptins is divided into three classes, alpha, beta, and gamma, with further subdivision into beta- and beta-prime components. Two beta-prime adaptins, the rat AP105a and the human BAM22, have previously been characterized. The BAM22 gene is located on human Chromosome (Chr) 22q12 and can be considered a candidate meningioma tumor suppressor gene. We report here the characterization of the mouse ortholog of the BAM22 gene, and we suggest the name adtb1 for the mouse gene. Like the BAM22 gene, the adtb1 transcript is highly and ubiquitously expressed. We provide 3885-bp cDNA sequence, which entirely covers the open reading frame of the adtb1, capable of encoding a protein of 943 amino acids. The adtb1 protein is highly conserved (>96% identity) when compared with AP105a and BAM22 proteins. We also report the genomic organization of adtb1, which is similar to the BAM22 gene. The adtb1 gene has been assigned to mouse Chr 11, band 11A2, which confirms the synteny between human Chr 22q12 and mouse Chr 11.