title: TspMI, a thermostable isoschizomer of XmaI (5'C/CCGGG3'): characterization and single molecule imaging with DNA.
abstract: TspMI, a thermostable isoschizomer of XmaI from a Thermus sp., has been characterized. The enzyme was purified to homogeneity using Cibacron-Blue 3GA agarose, Heparin agarose, SP sephadex C50, and Mono-Q fast protein liquid chromatography and was found to be a homodimer of 40 kDa. Restriction mapping and run-off sequencing of TspMI-cleaved DNA ends depicted that it cleaved at 5'C/CCGGG3' to generate a four-base, 5'-CCGG overhang. The enzyme was sensitive to methylation of second and third cytosines in its recognition sequence. TspMI worked optimally at 60 degrees C with 6 mM Mg(2+), no Na(+)/K(+), and showed no star activity in the presence of 25% glycerol. The enzyme could efficiently digest the DNA labeled with a higher concentration of YOYO-I (one dye molecule to one nucleotide), making it a useful candidate for real-time imaging experiments. Single molecule interaction between TspMI and lambda DNA was studied using total internal reflection fluorescence microscopy. The enzyme survived 30 polymerase chain reaction (PCR) cycles in the presence of 10% glycerol and 0.5 M trehalose without any activity loss and, hence, is suitable for incorporation in restriction-endonuclease-mediated selective-PCR for various applications.
authors.affiliation: Department of Microbiology, Panjab University, Chandigarh 160014, India.
authors.forename: Vijay
authors.initials: V
authors.lastname: Parashar
authors.forename: Neena
authors.initials: N
authors.lastname: Capalash
authors.forename: Shuang-Yong
authors.initials: SY
authors.lastname: Xu
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Sako
authors.forename: Prince
authors.initials: P
authors.lastname: Sharma
mesh_terms: D001665:Binding Sites; D004247:DNA / Q000378:metabolism*; D015257:DNA-Cytosine Methylases / Q000737:chemistry / Q000378:metabolism*; D004795:Enzyme Stability; D007527:Isoenzymes; D008745:Methylation; D013824:Thermus / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D004247:DNA; C079006:DNA modification methylase XcyI; D015257:DNA-Cytosine Methylases