Generalized organization of MCSG vectors. MCSG vectors encode an N-terminal leader sequence (arrow) that terminates in an LIC region centered on an SspI site. Restriction sites in and around the coding/cloning region allow insertion of protein or peptide modules into the leader (at BglII and/or KpnI), replacement of the his-tag (NdeI to BglII or KpnI), or transfer of the entire region to different backgrounds (NdeI to BamHI, HinDIII or XhoI). Derivatives (Table 7.1) add MBP, GST, or a loop of GroES (Sloop), replace the His-tag with the S-tag, and move these expression regions to pACY-CDuet-1 and pCDFDuet-1, allowing cotransformation with two or three vectors and coexpression of multiple proteins. Another modification, pMCSG19, positions untagged MBP followed by the TVMV protease recognition sequence (12) ahead of the His-tag, allowing in vivo removal of MBP by coexpressed TVMV protease.