Organization and gene expression within restriction-modification systems of Herpetosiphon giganteus.
We have characterized a family of related restriction-modification (R-M) systems from the soil bacterium Herpetosiphon giganteus (Hgi). A comparison of their genetic organization reveals two types of regulatory proteins, called controlling ORF C. While one of these small reading frames derived from RM.HgiCI seems to be an enhancer of its own promoter, evidence is provided for a silencer function of the other ORF C derived from the closely related AvaII-type systems RM.HgiBI/CII/EI. The respective silencer function is detected during our various attempts to clone three isoschizomers with unusually high differences in their specific activity. Sequencing and site-directed mutagenesis revealed just two amino acids as being responsible for a massive increase in specific activity of these endonucleases.
Kröger
M
M
Institut für Mikrobiologie and Molekularbiologie, Justus-Liebig-Universität Giessen, Germany.
Blum
E
E
Deppe
E
E
Düsterhöft
A
A
Erdmann
D
D
Kilz
S
S
Meyer-Rogge
S
S
Möstl
D
D
D001483:Base Sequence; D003001:Cloning, Molecular / Q000379:methods; D004262:DNA Restriction Enzymes / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015252:Deoxyribonucleases, Type II Site-Specific / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D015971:Gene Expression Regulation, Enzymologic; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D015183:Restriction Mapping; D013379:Substrate Specificity
D004262:DNA Restriction Enzymes; C051612:endodeoxyribonuclease BanI; D015252:Deoxyribonucleases, Type II Site-Specific