Nostoc PCC7524, a cyanobacterium which contains five sequence-specific deoxyribonucleases.

Five nucleotide sequence-specific deoxyribonucleases present in cell-free extracts of the filamentous cyanobacterium Nostoc PCC7524 have been purified and characterized. One of these enzymes, designated Nsp(7524)I cleaves at a new kind of nucleotide sequence, i.e. 5'-PuCATG Py-3'. The other four restriction enzymes in this organism, designated Nsp(7524)II, Nsp(7524)III, Nsp(7524)IV and Nsp(7524)V, are isoschizomers of enzymes which have been previously described. The cleavage site of Nsp(7524)II which is an isoschizomer of SduI was determined.