The "malE" gene, coding for MBP, belongs to the Mal regulon of "E. coli", which consists of ten genes whose products are geared for the efficient uptake and utilization of maltose and maltodextrins. All the gene involved in the transport of maltose/maltodextrin, including "malE", are clustered in the "malB" region of "E. coli" and organized in two divergent operons: "malE-malF-malG" and "malK-lamB". The transcription start sites at the "malEp" and "malKp" promoters are distant of 271 base pairs. The "malEp" and "malKp" promoters are synergistically activated by protein MalT, the activator of the Mal regulon and by the cAMP receptor protein CRP. This activation is a coupled process that involves, going from "malEp" towards "malKp": two MalT binding sites; three CRP binding site, and two overlapping sets of three MalT binding sites, staggered by three base pairs. Transcription activation requires the binding of adenosine triphosphate (ATP) and maltotriose to MalT and the binding of cyclic AMP to the dimer of CRP. The unliganded form of MalT is monomeric whereas its liganded form, in the presence of ATP and maltotriose, is oligomeric. One suspects that commercial maltose contains enough maltotriose for the induction of the Mal regulon. MBP is used to increase the solubility of recombinant proteins expressed in "E. coli". In these systems, the protein of interest is often expressed as a MBP-fusion protein, preventing aggregation of the protein of interest. The mechanism by which MBP increases solubility is not well understood. In addition, MBP can itself be used as an affinity tag for purification of recombinant proteins. The fusion protein binds to amylose columns while all other proteins flow through. The MBP-protein fusion can be purified by eluting the column with maltose. Once the fusion protein is obtained in purified form, the protein of interest (X) is often cleaved from MBP with a specific protease. Protein X can then be separated from MBP by affinity chromatography. A first study of the relations between structure and functions of MBP was performed by random insertion of a short DNA fragment, coding for a BamHI restriction site, into the "malE" gene.