tRNA (uracil-5-)-methyltransferase
tRNA (uracil-5-)-methyltransferase is an enzyme that catalyzes the transfer of a methyl group to uracil at the 5-position within transfer RNA (tRNA) molecules. This modification is a post-transcriptional process, meaning it occurs after the tRNA molecule has been transcribed from DNA. The enzyme utilizes a methyl donor, typically S-adenosylmethionine (SAM), to supply the methyl group.
The resulting 5-methyluridine (m5U) modification is found at position 54 of tRNA in a wide variety of organisms, from bacteria to eukaryotes. This specific location is within the TψC loop, a highly conserved region of tRNA that is crucial for its structural integrity and interactions with the ribosome.
The function of m5U modification is multifaceted. It plays a role in stabilizing the three-dimensional structure of tRNA, protecting it from degradation, and modulating its interactions with other cellular components, particularly the ribosome. This modification contributes to efficient and accurate translation by influencing codon recognition and tRNA binding to the ribosome.
Different tRNA (uracil-5-)-methyltransferases may exhibit specificity for particular tRNA isoacceptors (tRNAs that recognize the same codon). Loss or dysfunction of this enzyme can lead to defects in tRNA structure and function, potentially impacting protein synthesis and overall cellular homeostasis. Furthermore, alterations in tRNA modification patterns, including m5U, have been implicated in various diseases, including cancer and neurological disorders.