The ABC transporter superfamily is the largest family of proteins in all organisms. Many members of this family are medically relevant. A well-known eukaryotic member is the cystic fibrosis transmembrane conductance regulator, which if mutated, results in the cystic fibrosis disease. Some ABC transporters mediate multidrug and antibiotic resistance. The molybdate transporter is a member of the family. It provides the essential molybdenum cofactor to many molybdo-enzymes in bacteria, plants and animals. The human molybdoenzymes sulfite oxidase, xanthine dehydrogenase, and aldehyde oxidase catalyze a variety of oxidation/reduction reactions during human development. Defects in these enzymes can lead to neurological abnormalities, such as dislocated ocular lenses, and mental retardation, usually leading to death in early childhood. The long-term goal of the research project is to study the structural basis of molybdate transport using prokaryotic species as the model system for the human transporter. Knowledge of the three-dimensional structure of the molybdate transporter will enable design of efficient methods in administrating molybdate to patients with deficiency of molybdenum cofactor The structure will also add to our knowledge how the entire family of ABC transporters work ? ?