When produced on a large scale, recombinant proteins can prove to be invaluable tools for the facilitation of such processes as polymer degradation, remediation of toxic waste and the treatment of disease. However, the purification of proteins produced on a large scale can be problematic. Since protein concentrations in extracytoplasmic environments are extremely low relative to those found in the cytoplasm, as an initial step in the purification process, the biotech industry has made extensive use of secretory pathways, primarily the universally conserved Sec pathway, which secretes proteins in an unfolded conformation. Unfortunately, not all proteins fold properly in extracytoplasmic environments.  The twin arginine (Tat) pathway, which secretes proteins in a folded conformation, is an attractive alternative for transporting and secreting recombinant proteins that cannot fold properly in an extracytoplasmic environment.  While prokaryotes use the Tat pathway to varying extents, several organisms use it extensively.  In fact, in silico and in vivo data have shown that haloarchaea transport most secretory proteins via the Tat pathway. We are now attempting to determine the mechanisms that allow the haloarchaeon H. volcanii to use the Tat pathway to efficiently transport a large number of proteins. Moreover, we have characterized a broad range of substrates, including lipoproteins, that can be transported via the Tat pathway.  The information accumulated in our studies will likely hasten the development of the Tat pathway as a means for secreting properly folded, industrially relevant recombinant proteins, which will allow more efficient purification of these economically important proteins.