Provided are means for evaluating and identifying putative substrates of the twin arginine translocation (Tat) secretory pathway in Streptomyces and other bacterial species. Also provided, therefore, are simple ways to express, secrete and purify correctly folded heterologous proteins on a large scale using host microorganisms, such as, Streptomyces and the Tat pathway therein. Many of the thus-produced proteins are of significant therapeutic value in the pharmaceutical and biochemical industries, particularly when they can be secreted from the host in fully-folded active form. Accordingly, there are further provided the heterologous proteins produced by the Tat secretion pathway using the foregoing methods, and the computer algorithm used to identify the Tat signal sequence and putative substrates.
 This invention was supported in part by Grant Nos. T32GM-007229 from the National Institutes of Health, 0110093U from the American Heart Association, MCB 9816411 from the National Science Foundation and DE-FG02-01ER15169 from the Department of Energy. Accordingly, the Government may have certain rights in this invention.