23S rRNA (guanine748-N1)-methyltransferase

23S rRNA (guanine748-N1)-methyltransferase is an enzyme that catalyzes the N1-methylation of guanine at position 748 in the 23S ribosomal RNA (rRNA) molecule. This methylation is a post-transcriptional modification, meaning it occurs after the rRNA molecule has been transcribed from DNA. The enzyme uses a methyl group donor, typically S-adenosylmethionine (SAM), to transfer a methyl group to the N1 position of guanine748.

This methylation is crucial for ribosome function, specifically in the area of peptidyl transferase activity and antibiotic resistance. The presence of the methyl group at this specific location can influence the ribosome's ability to bind and process transfer RNA (tRNA) during protein synthesis.

Mutations or alterations in the 23S rRNA (guanine748-N1)-methyltransferase enzyme, or in the methylation site itself, have been linked to resistance to certain antibiotics, particularly macrolides, lincosamides, and streptogramin B (MLSB antibiotics). The methylation can sterically hinder the binding of these antibiotics to the ribosome, thus preventing them from inhibiting protein synthesis.

The enzyme is encoded by genes, such as erm genes (erythromycin resistance methylase), found in a variety of bacteria, often on plasmids or transposons, facilitating their spread and contributing to the increasing problem of antibiotic resistance. The specific erm gene and the resulting enzyme may exhibit some variations in their amino acid sequence, leading to slightly different substrate specificities or levels of antibiotic resistance conferred.