Molecular biology studies on M. feprae and M. tllberculosis involve cloningrnof genes and high level of expression to provide large amounts of protein.rnThese proteins are used 10 study their usefulness in sub-unit vacci nes or asrnantigens in diagnostic kits. Most of the work that has been done to obtainrnprotein antigens directly from the pathogens has drawbacks. For examplernthe tedious purification methods and the inability to culture M.leprae inrnvitro. Most of these obstacles can be circumvented by over-expressingrnproteins in E.coli but that has its drawbacks as well. The posHransiationairnmodification in Â£.coli is absent or at least different from that mrnmycobacteria. Furthcnnore, some mycobacterial proteins can not bernproduced in E.coli. We have init iated studies to develop a mycobacterialrnexpression vector th at might sidestep somc or the above namcd difficulties.rnThis study describes the construction or a vector that allows the overexpressionrnor mycobacterial proteins in a non-pathogenic, fast growingrnmycobacterial host. Firstly, we have cloned a number of model proteins inrnan E.coli expression system. These vectors allow the over-expression ofrnM.leprae and M.lllberclIlosis recombinant proteins (45kD, Esat-6 and Trx)rnin E. coli. Secondly, a mycobacteri al expression vector (pDKl) wasrnconstructed. This vector has a hi stidine-tag that can be used for affinityrnpurification or proteins. In this way we circumvent tedious biochemicalrnpurification systems. It also contains a multiple cloning site for convenientrncloning of genes or interest. Thirdly, this pDK I expression vector was usedrnto introduce the same test proteins as for the E.coli expression vector. Theserntest proteins were over-expressed in E. coli as well as in a mycobacterialrnhost. Both protein sets can be used to detcnnine whether there is anyrndifference in recombinant prote ins obtained from E.coli and the semiautologousrnsystem using M. smegmaris as a recombinant host.