Nucleic Acids Research, Vol 24, Issue 10 1799-1801, Copyright © 1996 by Oxford University Press
SG Welch and RA Williams
One hundred and forty eight isolates of the genus Thermus, from neutral and
alkaline hot water springs on four continents, have been screened for the
presence of restriction endonuclease activity. An isolate (SM49) from the
island of Sao Miguel, in the Azores, showed a high level of restriction
endonuclease activity when a cell-free extract was incubated with lambda
phage DNA at 65 degrees C. A Type II restriction endonuclease (Tsp49I) has
been partially purified from this isolate and the recognition and cleavage
site determined. Tsp49I recognizes the four base sequence ACGT, which is
the same as the recognition sequence of the mesophilic Type II restriction
endonuclease MaeII. However, unlike MaeII, which cleaves DNA between the
first and second bass of the recognition sequence (A/CGT), Tsp49I
hydrolyses the phosphodiester bond in both strands of the substrate after
the last base of the recognition sequence 5'-ACGT/-3', producing four base
3'-OH overhangs (sticky ends). The enzyme has a pH optimum of 9.0, requires
2 mM MgCl2 for maximum activity and retains full enzyme activity following
incubation for 10 min at temperatures up to 8O degrees C. Two further
examples of the same restriction endonuclease specificity as Tsp491 were
detected in Thermus isolates from Iceland (TspIDSI) and New Zealand
(TspWAM8AI). The three MaeII neoschizomers, Tsp49I, TspIDSI and TspWAM8AI,
exhibit similar pH optima, heat stabilities and MgCl2 requirements, but
differ in their requirements for NaCl and KCl.
ARTICLES
Tsp49I (ACGT/), a thermostable neoschizomer of the Type II restriction endonuclease MaeII (A/CGT), discovered in isolates of the genus Thermus from the Azores, Iceland and New Zealand
Department of Biochemistry, Faculty of Basic Medical Sciences, Queen Mary and Westfield College, University of London, UK.
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S. Welch, S al-Awadhi, and R. Williams Isoschizomers of the restriction endonuclease TaqI (T/CGA) requiring different metal ion concentrations and having a range of thermal stabilities from Thermus species from different continents Microbiology, January 1, 1998; 144(1): 167 - 175. [Abstract] |
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