methylases

methylases

host cell enzymes that introduce methyl groups into bases of DNA. In prokaryotic cells two methyl groups are introduced into the palindromic sequences by the restriction endonucleases that recognize the palindrome; when methylated, the restriction enzyme does not cut the DNA so that methylation protects host cell DNA from cleavage.
References in periodicals archive ?
In the first step of this cycle, the SAM-dependent methylases that use SAM as a substrate produce S-adenosyl homocysteine as a product.
The resistance is via three related genes, ermA, ermB, and ermC, which produce methylases that alter the targeted ribosome by methylating it.
Also plasmid-mediated methylases that cause resistance to all aminoglycosides have been encountered.
Site-specific methylases induce the SOS DNA repair response in Escherichia coli.
The activity of endogenous methylases in human placenta increased steadily with weeks of gestation, suggesting that increased formation of methyltransferases might occur during pregnancy (Paik et al.
24,25) Secondly, high-level macrolide resistance may result from modification of the drug target (ribosomal binding site) via erm(B) genes that encode 23S rRNA methylases, and lead to cross-resistance to the ML[S.
Like other methylases, Dam chemically coats DNA with clusters of atoms known as methyl groups.
In that study, ~2-5% of CCGG sites were fully methylated, suggesting that nuclear methylases enter a subset of the mitochondria.
16S rRNA methylases were found to confer high levels of resistance to aminoglycosides such as amikacin, tobramycin, and gentamicin.
Composite transposons and other genetic determinants also considered to be located in specific mobile elements such as macrolide (either encoding methylases [erm genes] or efflux pumps [mef genes]) and tetracycline resistance determinants (tet genes) have been found among streptococcal species of human origin.
These mechanisms include target site modification by methylases encoded by erm genes, in particular erm(A), erm(B), and erm(C).