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pst
PstI is a type II restriction endonuclease isolated from the Gram negative species, Providencia stuartii. It is the isoschizomer of Streptomyces albus P restriction enzyme SalPI. It cleaves DNA at the recognition sequence 5′-CTGCA/G-3′ generating fragments with 3′-cohesive termini. This cleavage yields sticky ends 4 base pairs long. PstI is catalytically active as a dimer. The two subunits are related by a 2-fold symmetry axis which in the complex with the substrate coincides with the dyad axis of the recognition sequence. It has a molecular weight of 69,500 and contains 54 positive and 41 negatively charged residues.
The PstI restriction/modification (R/M) system has two components: a restriction enzyme that cleaves foreign DNA, and a methyltransferase which protect native DNA strands via histone methylation. The combination of both provide a defense mechanism against invading viruses. The methyltransferase and endonuclease are encoded as two separate proteins and act independently. In the PstI system, the genes are encoded on opposite strands and hence must be transcribed divergently from separate promoters. The transcription initiation sites are separated by only 70 base pairs. A delay in the expression of the endonuclease relative to methylase is due to the inherent differences of the two proteins. The endonuclease is a dimer, requiring a second step for assembly, whereas the methylase is a monomer.
PstI is functionally equivalent to BsuBI. Both enzymes recognize the target sequence 5'CTGCAG. The enzyme systems have similar methyltransferases (41% amino acid identity), restriction endonucleases (46% amino acid identity), and genetic makeup (58% nucleotide identity). These observations suggest a shared evolutionary history.
When examining the preferential double strand cleavage of DNA, the restriction endonuclease PstI bind to pSM1 plasmid DNA.
Up for sale or trade is my LNIB Vortex Viper PST 2.5-10x32 FFP with EBR-1 MOA reticle. Never seen the range. Scope was mounted to a rifle that sat in the safe for a couple years. Great optic I’m just looking for something with a little more magnification. Comes with everything it came with from...
I bought this new about 6 months ago and have used it a couple of times on top of my 6.5 CM Bergara HMR and 308 Ruger Precision Rifle (both rifles also for sale). The quality of this scope (especially the glass) have exceeded my expectations, but my interests have changed.
The scope will come...
Black FN SCAR 17s with 4 Magazines, Vortex Viper PST 2.5-10x scope, LaRue QD scope mount and vertical grip with spring-loaded bipod and flashlight.. Rifle is in excellent condition with 400 rounds through her. $4000 Reduced to $3800!
I will also accept trade + cash of Arsenal AK or...
Vortex Viper PST Gen II 5-25x50 Riflescope FFP MRAD EBR-2C for sale at $900
Upgraded to a Vortex Razor HD.
Been a great scope. Comes with the original box and paperwork and Vortex' amazing lifetime warranty. Has lived on my Bergara B14 HMR this year and has performed flawlessly for my 600 yard...
Selling my Vortex Viper PST 2.5-10x32 FFP MRAD scope WITHOUT the ADM recon mount for $600
Comes with the original box and paperwork with the brass zero-stop shims and Vortex' amazing lifetime warranty. Has lived on my BCM 16" middy for the last couple years and has performed flawlessly but I...
LNIB, mounted but never got around to sighting it in or shooting with it. Still have original box, caps, lens cloth still in plastic. $375/OBO shipped-No Trades; PayPal accepted. Pics are up, email or IM me if interested.
Received this scope in a trade and ended up not using it, hoping to find a loving home for it!
Vortex Viper PST 4-16x50 EBR-1 (mrad reticle)
There is a small blemish on the bottom of the optic but other than that it is essentially new.
Comes in original packaging and includes sun-shade...
Never removed from the package, brand spanking NIB Vorter Viper PST Gen II 5-25x50mm FFP (first focal plane) EBR-2C in Mil (MRAD).
30mm Tube, illuminated reticle, zero stop turrets, scope caps included
asking $860 shipped (insurance extra)
* item is cross posted
For sale, a like new (used 5 times on the range) Vortex Viper Gen 2 PST 1-6x24mm MOA in a KDG SideLok 30mm mount. Have all the original packaging and paperwork.
Price $700 for the whole setup.
**Only trade would be toward a 9mm handgun (EDC) plus cash**
Location: Tacoma, Wa area.
Vortex Viper PST 4-16x50. EBR1 MRAD illuminated reticle. Elevation and wind age turrets as well as side focus. Comes with sun shade and lens covers. Great shape. Nothing wrong with it. $550