Patent ID: 8623652

Claim:
A system for cloning and/or expressing a target gene comprising: a host comprising: a T7 RNA polymerase gene configured to produce a T7 RNA polymerase protein, the T7 RNA polymerase gene including: a T7 RNA polymerase coding sequence; a first promoter operationally linked to the T7 RNA polymerase coding sequence; and a first lac operator operationally linked to the promoter; a single copy of a lacI gene configured to produce an amount of lac repressor protein including: a lacI coding sequence; a second promoter operationally linked to the lacI coding sequence, wherein the second promoter comprises nucleotides 1-56 of SEQ ID NO:4; and a translational enhancer sequence comprising a sequence at least about 90% identical to nucleotides 62-71 of SEQ ID NO:4 or comprising a sequence selected from the group consisting of TTAACTTTA, TTAACTT, TTAACT, ACTTTA, AATTTTA, GGCTTT, AACTTTG, AACTTT, and TAACTTTA; and a T7 plasmid vector for transforming into the host comprising: a target gene insertion site; a T7 promoter operationally linked to the target gene insertion site; and a second lac operator operationally linked to the T7 promoter, wherein the T7 plasmid vector is devoid of a gene for expressing lac repressor; wherein the amount of lac repressor protein inhibits expression of the target gene in the absence of inducer and permits at least a 10-fold increase in expression of the target gene in the presence of inducer.