Periplasmic secretion fusion expression type pre-T vector, preparation and application

The invention provides a periplasmic secretion fusion expression pre-T vector, which is prepared by the following method: firstly, a DNA1 fragment of BspTI-GSGSG-HHHHHH-XcmI-Amp-XcmI-HindIII is established and encoded; secondly, the DNA sequence of three XcmI sites in an LacI gene in a site-directed mutation pET39 plasmid is changed under the condition that the encoding amino acid sequence is unchanged, so as to lose XcmI recognition sites, and site-directed mutation pET39' which eliminates the XcmI sites is obtained; and thirdly, DNA1 is directionally recombined into the pET39' by utilization of BspTI and HindIII, and the periplasmic secretion fusion expression pre-T vector is obtained. Besides the XcmI for preparing a linear T vector, the invention does not need to use other restriction enzymes, can further establish fusion expression genetic engineering bacteria in one step, and provides a feasible technical method for preparing a plurality of bioactive peptide engineering bacterium libraries.