Restriction/Modification Systems of Pneumococci: Why Two Methylases in the DpnII System?
- Brookhaven National Laboratory (BNL), Upton, NY (United States)
The systems for DNA restriction and modification in Streptococcus pneumoniae are unusual in three respects. First, the DpnI restriction endonuclease only acts on a methylated site in DNA. Since DpnI attacks only methylated DNA, cells that make it do not require modification of their DNA. Second, strains of S. pneumoniae that do not harbor DpnI contain a complementary restriction system, that of DpnII. The DpnI and DpnII systems are mutually exclusive because DNA from a DpnI strain, which is not methylated at 5'-GATC-3' sites, is susceptible to DpnII, and DNA from a DpnII strain, which contains 5'-GmeATC-3', is susceptible to DpnI. Third, genetic and biochemical analysis of the DpnI and DpnII systems revealed an additional, unexpected protein in each of the restriction systems. In the DpnII system three proteins are produced, whereas in a typical restriction system, which like DpnII cleaves at unmethylated sites, only two proteins are generally found - the restriction endonuclease and a modification methylase. The function and significance of the additional protein in the DpnII system will be a major focus of this chapter.
- Research Organization:
- Brookhaven National Laboratory (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE; United States Department of Health and Human Services (HHS)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6012341
- Report Number(s):
- BNL--45931; CONF-9006331--1; BIO--4625; ON: DE91010372; CNN: GM29721
- Journal Information:
- Genetics and Molecular Biology of Streptococci, Lactococci, and Enterococci, Journal Name: Genetics and Molecular Biology of Streptococci, Lactococci, and Enterococci
- Publisher:
- American Society for Microbiology
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
BACTERIA
BIOLOGICAL FUNCTIONS
CHEMICAL REACTIONS
DNA
DNA METHYLASES
DNA-ASE
ENDONUCLEASES
ENZYMES
ESTERASES
FUNCTIONS
GENES
HYDROLASES
LYASES
METHYLATION
MICROORGANISMS
MOLECULAR BIOLOGY
NUCLEIC ACIDS
NUCLEOPROTEINS
ORGANIC COMPOUNDS
PHOSPHODIESTERASES
PROTEINS
STREPTOCOCCUS