Xba I recognizes the sequence T↓*CTAGA and generates fragments with 5′-cohesive termini. The enzyme needs at least two nucleotides around the target sequence before it will cut the cleavage site.
Compatible ends
Xba I ends are compatible with fragments generated by Avr I, Nhe I, and Spe I.
Isoschizomers
The enzyme is not known to have isoschizomers.
Methylation sensitivity
Xba I digestion of DNA is inhibited by the dam gene product of E. coli, which methylates the 6N position of adenine in the sequence GATC. The enzyme is also inhibited by 5-methylcytosine or 5-hydroxymethylcytosine at the site (*) indicated on the recognition sequence.
Activity in SuRE/Cut Buffer System
Buffer printed in bold face type is the buffer recommended for optimal activity:
A B L M H
100% 75-100% 75-100% 75-100% 100%
Relative activity in complete PCR mix
Relative activity in PCR mix (Taq DNA Polymerase buffer) is 60%. The PCR mix contained ?DNA, primers, 10 mM Tris-HCl (pH 8.3, +20°C), 50 mM KCl, 1.5 mM MgCl2, 200 ?M dNTPs, 2.5 U Taq DNA polymerase. The mix was subjected to 25 amplification cycles. Activity in reaction buffer of Pwo SuperYield DNA Polymerase PCR Mix is 25%. When supplemented with GC-RICH Solution, activity increases to 100%.
Incubation temperature
+37°C
Number of cleavage sites on different DNAs
λ Ad2 SV40 ?X174 M13mp7 M13mp18 pBR322 pBR328 pUC18
1 5 0 0 0 1 0 0 1
PFGE tested
Xba I has been tested in Pulsed-Field Gel Electrophoresis (on bacterial chromosomes). For cleavage of genomic DNA (E. coli C 600) embedded in agarose for PFGE analysis, we recommend 10 U enzyme per ?g DNA and approximately 4 hour incubation time.
Ligation and recutting assay
Xba I fragments obtained by complete digestion of 1 ?g pUC18 DNA are ligated with 1 U T4 DNA Ligase in a volume of 10 ?l by incubation for 16 hours at +4°C in 66 mM Tris-HCl, 5 mM MgCl2, 5 mM Dithiothreitol, 1 mM ATP, pH 7.5 (at +20°C) resulting in >90% recovery of pUC18 DNA.
Subsequent re-cutting with Xba I yields >95% of the typical pattern of pUC18 × Xba I fragments.
