tRNA-guanine transglycosylase
Overview
tRNA-Guanine Transglycosylase (TGT) is an enzyme that modifies tRNA molecules by exchanging guanine at position 34 of the anticodon loop with queuine, a hypermodified base. This post-transcriptional modification is critical for tRNA functionality in translation, particularly in bacteria and eukaryotes. TGT is studied for its role in microbial virulence, making it a potential target for antibiotic development. First identified in the 1970s, TGT exhibits species-specific variations. Bacterial TGTs are structurally simpler than their eukaryotic counterparts, which often form complexes with auxiliary proteins. The enzyme’s mechanism involves a two-step transglycosylation reaction, requiring magnesium ions for activity.
Physical and Chemical Properties
TGT is a monomeric or dimeric protein with a molecular weight ranging from 45 to 50 kDa, depending on the organism. Its active site contains a conserved aspartate residue critical for catalysis. The enzyme operates optimally at neutral pH (7.0–7.5) and requires Mg2+ as a cofactor. Stability varies by source: bacterial TGTs are generally more robust than eukaryotic versions, retaining activity after lyophilization. Solubility is high in standard biochemical buffers, but prolonged storage at room temperature leads to denaturation. Spectrophotometric assays (e.g., absorbance at 280 nm) are commonly used to quantify purity.
Main Applications
TGT is primarily used in academic and industrial research to study tRNA modification pathways. Its bacterial form is a validated drug target; inhibitors could lead to novel antibiotics against pathogens like Shigella flexneri. In biotechnology, engineered TGT variants assist in synthesizing queuosine-containing tRNAs for structural studies. The enzyme also serves as a model system for investigating transglycosylation mechanisms. Pharmaceutical companies screen TGT inhibitors using high-throughput assays, leveraging its conserved active site for broad-spectrum drug design.
Safety and Storage
TGT poses minimal biosafety risks but should be handled following BSL-1 guidelines. Use gloves and eye protection to prevent contamination. Lyophilized powder is stable at -20°C for years; solutions retain activity for months at -80°C if aliquoted to avoid freeze-thaw cycles. Avoid repeated exposure to light or oxidizing agents, which may degrade the enzyme. For long-term storage, add glycerol (10–20%) to solutions. Discard if precipitation or loss of activity (measured by standard enzymatic assays) is observed.
B2B Procurement Guide
When procuring TGT, specify the organism source (e.g., E. coli, human recombinant) and purity level (≥90% for most assays). Reputable suppliers provide certificates of analysis including activity units (e.g., µmol/min/mg). Bulk orders (10+ mg) may qualify for discounts. For drug discovery projects, consider inhibitor screening kits that include TGT and substrates. Compare lead times—custom recombinant expressions may take 4–6 weeks. Validate shipments upon arrival using SDS-PAGE or activity tests to ensure compliance with research needs.