title: Eight new restriction endonucleases fröm Herpetosiphon giganteus--divergent evolution in a family of enzymes.
abstract: Characterization of eight restriction endonucleases isolated from five strains of Herpetosiphon giganteus is described. HgiCI from strain Hpg9 recognizes and cleaves the degenerate sequence: GGPyPuCC, producing 5'-hexanucleotide protruding ends. Endonucleases HgiBI, HgiCII and HgiEI are isoschizomers of AvaII; HgiCIII and HgiDII are isoschizomers of SalI; and HgiDI and HgiGI are isoschizomers of AcyI. Based upon their closely related and in part overlapping recognition specificities a close evolutionary relationship is proposed for all known Hgi restriction endonucleases.
mesh_terms: D001483:Base Sequence; D005075:Biological Evolution; D041964:Cytophagaceae / Q000201:enzymology / Q000235:genetics*; D004247:DNA / Q000235:genetics; D004262:DNA Restriction Enzymes / Q000235:genetics* / Q000302:isolation & purification; D009690:Nucleic Acid Conformation; D013045:Species Specificity; D013379:Substrate Specificity
chemical_list: D004247:DNA; D004262:DNA Restriction Enzymes