23S rRNA (adenine2503-C8)-methyltransferase

23S rRNA (adenine2503-C8)-methyltransferase is an enzyme that catalyzes the methylation of adenine at position 2503 on the C8 atom of the 23S ribosomal RNA (rRNA) molecule. This modification is a form of post-transcriptional modification that occurs within the ribosome.

Specifically, the enzyme uses a methyl group donor, typically S-adenosylmethionine (SAM), to transfer a methyl group to the adenine base at position 2503 of the 23S rRNA. The resulting methylated adenine is referred to as m8A2503.

This methylation modification is crucial for ribosome function and antibiotic resistance in certain bacterial species. The m8A2503 modification is often located in the peptidyl transferase center (PTC) of the ribosome, a region responsible for peptide bond formation during protein synthesis. Methylation at this site can alter the binding affinity of certain antibiotics, particularly macrolides, lincosamides, and streptogramin B (MLS) antibiotics, thereby conferring resistance.

Different bacterial species may utilize different 23S rRNA (adenine2503-C8)-methyltransferases, often encoded by genes such as erm (erythromycin ribosome methylase) genes. These genes can be located on plasmids or chromosomes and their expression leads to resistance against MLS antibiotics. The presence and expression of these methyltransferases can significantly impact the effectiveness of these antibiotics in treating bacterial infections.

The mechanism of action of the enzyme involves recognizing the specific sequence and structure of the 23S rRNA around adenine 2503 and then precisely transferring the methyl group. Understanding the structure and function of these methyltransferases is important for developing strategies to combat antibiotic resistance.