Bw. Soper et al., CHARACTERIZATION OF ADDITIONAL HOST RESTRICTION-MODIFICATION SYSTEMS IN THE UNICELLULAR CYANOBACTERIUM CYANOTHECE SP, Biochemical and biophysical research communications, 223(1), 1996, pp. 24-30
In order to develop a gene transfer system for the unicellular diazotr
ophic cyanobacterium Cyanothece sp. strain BH68K, this organism has be
en further investigated for the presence of additional host restrictio
n-modification enzymes other than Csp68KI, previously reported for Cya
nothece sp. Analysis of cell extracts by phosphocellulose and Mono Q f
ast protein liquid chromatography (FPLC) has led to the identification
of three new restriction endonucleases. These enzymes have been desig
nated Csp68KII, Csp68KIII, and Csp68KVI. Csp68KII is an isoschizomer o
f AsuII and restricts DNA at the recognition sequence 5'-TT/CGAA-3'. C
leavage occurred between thymine and cytosine producing 2 bp 5' overha
ng ends. The third restriction endonuclease, Csp68KIII, is an isoschiz
omer of AvaIII and restricts DNA at the recognition sequence 5'-ATGCA/
T-3'. Cleavage occurred between the 3' adenosine and thymine nucleotid
es producing 4 bp 3' overhang ends. The fourth enzyme identified, Csp6
8KVI, recognizes CGCG and cleaves this sequence between the internal g
uanine and cytosine nucleotides producing blunt ends. (C) 1996 Academi
c Press, Inc.