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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.
Used PST Gen II, comes with Vortex throw lever, flip caps, sunshade, manual, Allen key, and Midwest Industries 30mm mount; all leveled up. This optic was on a bench DMR, got some other glass to replace it.
No trades, looking for sale only. Price includes shipping cost.
This is an Illuminated, FFP (First Focal Plane) mil (MRAD) scope. Great for PRS/NRL style competitions or long range shooting.
It's in excellent condition with scope cover, sunshade and box. This is the newer EBR-7C mil reticle.
Used on a 22lr for a while. The rings are the burris signature zee...
New condition/mocked up in mount only. Paid over 1000 a month or two back. Japanese glass is extremely clear. Only reason selling is going to run 1-8.
Will throw in Midwest industries mount in for 100 if interested.
Springfield Saint Edge Rifle
Vortex Viper PST Gen II 1-6x24mm w/throw lever
Magpul MBUS Pro Offset sights
Magpul M-lok QD Mount
Magpul MS1 Sling
Swapped BCM Mod 0 for B5 Systems Bravo Stock (QD mount on BCM drove me nuts)
1-10rd gen3 Pmag
9-30rd gen3 Pmags (Not available for WA residents)
For Sale: $800 includes all the extras listed
VORTEX, VIPER PST GEN II 3-15X44 FFP EBR-7C MOA
Part Number: PST-3156
Magnification: 3-15 X
Objective Lens Diameter: 44 MM
Eye Relief: 3.4
Field of View: 41.2 - 8.6' @ 100 yds
Tube Size: 30 mm
Adjustment Graduation:1/4 MOA...
Very nice condition Vortex Viper PST 6-24x50 FFP Gen1 in MRAD.
Comes with Vortex throw lever and bubble level along with see through flip caps on objective and ocular lenses. Glass is excellent, turret adjustments are solid and tactile, finish is still very nice. A great all around high...
Vortex Viper gen1 PST 6-24x50 FFP MRAD.
Comes with LaRue LT111 OBR qd mount, Vortex Bubble Level, Vortex throw lever, see through flip caps.
Everything is in very nice condition. Very minor handling marks, glass is in excellent condition.
Only issue is illumination is very dim when turned on...
Nice optic, still have another at home here. This is extra and was on that sig upper I have for sale both fired under 40 rounds.
red illumination with variable brightness
comes with see thru lens caps, MKM throw lever, Redfield Tactical SPR Mount (knobs, may have some wear from...
For sale is a Gen 1 6-24x50 Vortex Viper PST first focal plane scope with the EBR-1 (MOA) Reticle. Almost pristine condition with very few rounds fired underneath it (around 150). Very minor (barely noticeable) ring marks on tube. $350
Also for sale are the badger ordnance rings as seen in the...
vortex viper pst 6x24x50
illuminated ebr-1c mrad reticle
first focal plane
warne maxima scope rings
includes all packaging sunshade lense cover etc
only trade interests
I will add cash on my end trades for custom actions ex. kelbly, stiller, arc, bighorn, etc. or...
SOLD to @Lazyfaire!
Up for sale is a Vortex Viper PST 4-16x50 2nd Focal Plane with illuminated EBR-1 MOA Reticle. 30mm tube. 1/4 MOA turrets.
Comes with original box, paperwork, sunshade, zero stop shims, vortex logo pin and bikini covers.
100% mechanical function. Scope tracks and holds...
I'm happy to announce the tentative date and time of the Northwest Firearms V4 Upgrade is Monday, July 15th, beginning at 3AM PST. While we hope get the site back up and running as soon as possible, it's hard to predict exactly how long the site will be down. If everything goes as planned it...
Up for sale is a Vortex PST Gen I 6-24 EBR-2C FFP MRAD. Been on the rifle for 2 years, still in near perfect condition. Comes with a lot of shims. Also comes with Butler Creek rear flip cap, and Vortex Switchview magnification lever. No front cap. $400 firm. Not looking for trades unless it’s a...