This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: peptidyl tranferase center modification
|Superclasses:||Detoxification → Antibiotic Resistance|
Expected Taxonomic Range:
The Cfr methyltransferase confers combined resistance to five classes of antibiotics that bind to the peptidyl transferase center of bacterial ribosomes by catalyzing methylation of the C-8 position of 23S rRNA nucleotide A2503. These five different classes of antibiotics include phenicols, lincosamides, oxazolidinones, pleuromutilins, and streptogramin A antibiotics [Long06]. These include the entirely synthetic oxazolidinone antibiotic linezolid, an important therapeutic option and often the last line of defense in the treatment of infections caused by MRSA [Toh07]. It is also known that Cfr expression confers resistance to the 16-membered macrolides josamycin and spiramycin [Smith08]. Thus, the Cfr-mediated resistance functions in both Gram-positive and Gram-negative bacteria and includes important antimicrobial agents that are currently used in human and/or veterinary medicine.
The cfr gene was originally detected on the pSCFS1 plasmid from Staphylococcus sciuri [Schwarz00] The gene encodes a methyltransferase that catalyzes the methylation of the C-8 carbon of adenosine at position 2503 of 23S rRNA [Kehrenberg05, Giessing09]. Some bacteria already have one methyltransferase (RlmN) that methylates adenosine 2503 at the 2 position (see EC 18.104.22.168, 23S rRNA (adenine2503-C2)-methyltransferase). Cfr can methylate either unmodified residues, or ones that have already been methylated at position 2 by RlmN.
The mechanism of action has been studied in detail. The newly introduced methyl group is assembled from an S-adenosyl-L-methionine (SAM)-derived methylene fragment and a hydrogen atom that had migrated from the substrate amidine carbon. Rather than activating the adenosine nucleotide of the substrate by hydrogen atom abstraction from an amidine carbon, the 5'-deoxyadenosyl radical abstracts hydrogen from the second equivalent of SAM to form the SAM-derived radical cation. This species, or its corresponding sulfur ylide, subsequently adds into the substrate, initiating hydride shift and S-adenosylhomocysteine elimination to complete the formation of the methyl group [Yan11a].
Giessing09: Giessing AM, Jensen SS, Rasmussen A, Hansen LH, Gondela A, Long K, Vester B, Kirpekar F (2009). "Identification of 8-methyladenosine as the modification catalyzed by the radical SAM methyltransferase Cfr that confers antibiotic resistance in bacteria." RNA 15(2);327-36. PMID: 19144912
Kaminska10: Kaminska KH, Purta E, Hansen LH, Bujnicki JM, Vester B, Long KS (2010). "Insights into the structure, function and evolution of the radical-SAM 23S rRNA methyltransferase Cfr that confers antibiotic resistance in bacteria." Nucleic Acids Res 38(5);1652-63. PMID: 20007606
Kehrenberg05: Kehrenberg C, Schwarz S, Jacobsen L, Hansen LH, Vester B (2005). "A new mechanism for chloramphenicol, florfenicol and clindamycin resistance: methylation of 23S ribosomal RNA at A2503." Mol Microbiol 57(4);1064-73. PMID: 16091044
Long06: Long KS, Poehlsgaard J, Kehrenberg C, Schwarz S, Vester B (2006). "The Cfr rRNA methyltransferase confers resistance to Phenicols, Lincosamides, Oxazolidinones, Pleuromutilins, and Streptogramin A antibiotics." Antimicrob Agents Chemother 50(7);2500-5. PMID: 16801432
Schwarz00: Schwarz S, Werckenthin C, Kehrenberg C (2000). "Identification of a plasmid-borne chloramphenicol-florfenicol resistance gene in Staphylococcus sciuri." Antimicrob Agents Chemother 44(9);2530-3. PMID: 10952608
Smith08: Smith LK, Mankin AS (2008). "Transcriptional and translational control of the mlr operon, which confers resistance to seven classes of protein synthesis inhibitors." Antimicrob Agents Chemother 52(5);1703-12. PMID: 18299405
Toh07: Toh SM, Xiong L, Arias CA, Villegas MV, Lolans K, Quinn J, Mankin AS (2007). "Acquisition of a natural resistance gene renders a clinical strain of methicillin-resistant Staphylococcus aureus resistant to the synthetic antibiotic linezolid." Mol Microbiol 64(6);1506-14. PMID: 17555436
Miller00a: Miller JR, Busby RW, Jordan SW, Cheek J, Henshaw TF, Ashley GW, Broderick JB, Cronan JE, Marletta MA (2000). "Escherichia coli LipA is a lipoyl synthase: in vitro biosynthesis of lipoylated pyruvate dehydrogenase complex from octanoyl-acyl carrier protein." Biochemistry 39(49);15166-78. PMID: 11106496
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