This vector contains the T7 promoter and a Lac operator binding site to allow regulated and inducible protein expression in E.coli. The promoter is upstream of the main multiple cloning site to drive gene expression.
Product Name: pSF-T7_LacO
Product Code: OG500
Size (bp): 5402 bp
Bacterial Antibiotic Selection: KanR
Origin and Compatibility: pUC high copy derived from pBR322
Bacterial Copy Number: 500-700 per cell
This is a bacterial expression plasmid containing T7 promoter that can be regulated using the Lac repressor. This allows for greater control over expression in comparison to normal T7 promoter plasmids. In order to use this plasmid you will require a T7 polymerase expressing E.coli cell line that also expresses the LacI repressor. A common expression cell line that can be used for this purpose is the BL21 (DE3) strain.Promoter Expression Level:
This plasmid contains the IPTG inducible promoter that was created by the fusion of the Lac promoter and the Tryptophan operon promoter. It allows inducible expression in E.coli using IPTG as the inducing agent.
This plasmid contains three alternative transcription terminators for Tag T7 LacO Inducible bacterial and bacteriophage (T7) expression. This means that only the promoter needs to be changed to alter the expression system you are using. We sell multiple promoters that can be used in each of these systems. The presence of each terminator does not reduce expression in the alternative systems.
This plasmid has been designed to be compatible with a range of cloning techniques. The multiple cloning site contains a range of standard commonly used restriction sites for cloning. Using these sites genes can be inserted using standard cloning methods with DNA ligase. Other methods such as ligase independent cloning (LIC) Gibson Assembly InFusionHD or Seamless GeneArt can also be used and because all of our plasmids are based on the same backbone the same method can be used for cloning into all of our catalogue vectors.Multiple cloning site notes:
There are a few important sites within the MCS. These include the NcoI site the XbaI site and the BsgI and BseRI sites. The NcoI site contains a start codon that is immediately downstream of both a Kozak and Shine-Dalgarno ribosomal binding site. These allow for optimal positioning of genes when the start codon is placed in this location. If this is not required and you wish to use a downstream site for gene cloning you can remove the NcoI site by cleaving the plasmid with KpnI.
The XbaI site contains a stop codon. This stop codon is positioned in a specific position in relation to the BsgI and BseRI sites that are immediately downstream. When either BseRI or BsgI cleave the plasmid they produce a TA overhang from the stop codon in the XbaI site that is compatible with all of our peptide tag plasmids cut with the same sites. BseRI and BsgI sites are non-palindromic and cleave a defined number of bases away from their binding site.
Whenever we clone a gene into our multiple cloning site we always position the start and stop codon in the same positions in the MCS. If the start and ends of the genes are not compatible with NcoI and XbaI we extend the sequence to the nearest external sites but keep the start and stop codons locations consistent.1: SnapFusion Cloning:
If you would like to fuse your coding sequence to the tag with minimal additional bases you can use our SnapFusion technology. This process involves amplifying your gene by PCR to add specific restriction sites onto the ends. When these sites are cut they produce an overhang that is compatible with this plasmid cut with BseRI or BsgI.To insert your gene:
1: Amplify your gene with primers designed using this spreadsheet
2: Cut the plasmid with either BseRI or BsgI.*
3: Cut your gene with the enzyme you added using the spreadsheet (any of AcuI BpmI BpuEI BseRI BsgI EciI).
4: Clone the gene into the plasmid using DNA ligase.
Using this method with an N-terminal tag plasmid will result in the tag coding sequence immediately followed by your genes ATG start codon at the join. This results in a seamless fusion of the two sequences with no extra bases being added. Using this method on C-terminal tag plasmids will convert your genes stop codon into a TAC (Tyr Y) codon followed by the plasmid tag coding sequence. This results in no extra bases between your gene and the tag. See the diagram below for more information.
*Please note that insect expression plasmids cannot be cut with BsgI only BseRI because of unavoidable conflicting sites in the backbone. Also Yeast plasmids cannot be cut with BseRI because of unavoidable restriction sites in the backbone.
Using this technique will create a gene fragment that can be ligated into any or our >1500 peptide and reporter tag plasmids. If you use one of the other techniques below (Gibson InFusion Seamless or LIC) you will need new primers for every vector you clone into because the arms of homology will change according to the tag plasmid you are cloning into.
If you find that your gene sequence has sites in it that make using this cloning strategy difficult you can still use one of the alternative methods below (e.g. standard cloning or Gibson cloning).
Open the Primer Design Tool to help you design primers for cloning your gene in our SnapFusion technique.2: Standard Enzymes:
If you are not concerned about leaving a few extra bases between the tag coding sequence and your gene you can clone your gene into the vector using standard cloning restriction enzymes. This strategy will require you to choose which enzymes you want to use to clone your gene.
Open the Primer Design Tool which provides primers with different enzyme choices positioning your gene as close to the tag as possible in each case. Please note that standard enzymes will always leave additional nucleotides between your gene and the tag but using the spreadsheet will ensure the tag and gene are in frame.3: Gibson cloning/InfusionHD/GeneArt Seamless/Ligase Independent Cloning (LIC) Methods:
These cloning techniques use reagents sold by other companies and allow you to fuse sequences together using enzymes that chew back the DNA to leave overlapping ends/overhangs. The subsequent method of joining the DNA depends on the kit used. To use one of these techniques you can either design your own primers or you can use the spreadsheet below to help with the design.
Open the Primer Design Tool to help you design primers for cloning your gene using Gibson assembly InfusionHD GeneArt Seamless cloning or Ligase Independent Cloning (LIC) techniques.
This product is part of our SnapFast™ plasmid range, for more information on the intellectual property status of this plasmid and the terms of our licences please click here.