Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.1.1.113 (restriction-modification system)
 350 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fibrobacter succinogenes is an important cellulolytic bacterium found in the rumen and cecum of herbivores. Numerous attempts to introduce foreign DNA into F. succinogenes S85 have failed, suggesting the presence of genetic barriers in this organism. Results from this study clearly demonstrate that F. succinogenes S85 possesses a type II restriction endonuclease, FsuI, which recognizes the sequence 5'-GG(A/T)CC-3'. Analysis of the restriction products on sequencing gels showed that FsuI cleaves between the two deoxyguanosine residues, yielding a 3-base 5' protruding end. These data demonstrate that FsuI is an isoschizomer of AvaII. A methyltransferase activity has been identified in the cell extract of F. succinogenes S85. This activity modified DNA in vitro and protected the DNA from the restriction by FsuI and AvaII. DNA modified in vivo by a cloned methylase gene, which codes for M.Eco47II, also protected the DNA from restriction by FsuI, suggesting that FsuI is inhibited by methylation at one or both deoxycytosine residues of the recognition sequence. The methyltransferase activity in F. succinogenes S85 is likely modifying the same deoxycytosine residues, but the exact site(s) is unknown. A highly active DNase (DNase A) was also isolated from the cell extract of this organism. DNase A is an endonuclease which showed high activity on all forms of DNA (single stranded, double-stranded, linear, and circular) but no activity on RNA. In vitro, the DNase A hydrolyzed F. succinogenes S85 DNA extensively, indicating the lack of protection against hydrolysis by this enzyme. In the presence of Mg2+, DNA was hydrolyzed to fragments of 8 to 10 nucleotides in length. The presence of DNase A and the type II restriction-modification system of F. succinogenes S85 may be the barriers preventing the introduction of foreign DNA into this bacterium.
 ...
PMID:Type II DNA restriction-modification system and an endonuclease from the ruminal bacterium Fibrobacter succinogenes S85. 164 54

Transformation (i.e., DNase-sensitive genetic transfer) of strains of Streptococcus mutans representing serotypes c and e was accomplished by using chromosomal DNA from a Rifr Strr Spcr isolate of strain GS5 (UAB525) and a chimeric plasmid, pYA629. Shuttle plasmid pYA629 comprises the S. mutans plasmid pVA318, an inducible erythromycin resistance determinant originally isolated from a group A streptococcal strain, the tetracycline resistance gene and replication region of the Escherichia coli plasmid pBR322, and the promoter region of the S. mutans gene for aspartate beta-semialdehyde dehydrogenase. The strains examined for recipient ability included those known to lack a cryptic plasmid (GS5, UA130, UA159, and MT8148) and those known to contain a widely disseminated 5.8-kilobase cryptic plasmid (LM7, V318, UA101, UA174, and 3098791). The transformation frequencies in GS5 for GS5 chromosomal antibiotic resistance markers were comparable to those reported by others, but UA101, UA130, UA159 and UA174 were transformed with both chromosomal and plasmid markers at much higher efficiencies. In a larger strain survey, strains containing the 5.8-kilobase cryptic plasmid were more frequently transformable with both chromosomal and pYA629 DNAs than were strains lacking this cryptic plasmid. All plasmid-containing strains except LM7 lost their resident cryptic plasmids when transformed with pYA629. LM7 transformed with pYA629 retained pLM7. There are therefore at least two incompatibility groups among S. mutans cryptic plasmids. yPA629 DNA isolated from either E. coli or S. mutans transformed S. mutans with equal efficiency. pYA629 DNA isolated from S. mutans transformed both restriction-deficient and restriction-proficient E. coli recipients. Therefore, the strains of S. mutans used lack a restriction-modification system for pYA629 DNA sequences. S. mutans strains that are readily transformable, display maximal cariogenicity in gnotobiotic rats, and give high scores for in vitro measures of important virulence attributes have been identified to facilitate studies on the genetic basis and control of virulence.
 ...
PMID:Transformation of Streptococcus mutans with chromosomal and shuttle plasmid (pYA629) DNAs. 302 26