DTWD1

Model summary

A soluble human enzyme that installs an aminocarboxypropyl group onto uridine within structured tRNA, using a soluble catalytic core to recognize RNA and transfer a non-methyl alkyl group from an activated donor. It operates primarily in the nucleus but can associate peripherally with membranes and shuttle through the cytoplasm, coordinating with tRNA biogenesis and maturation pathways. By executing this site-specific chemical modification, it contributes to the broader program of tRNA processing and the fidelity of RNA-based translation.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The polypeptide carries IPR051521 (tRNA-uridine aminocarboxypropyltransferase 1/YIPF3 family) spanning residues 24–299, which frames the entire catalytic core and specifies a lineage that modifies tRNA by transferring a non-methyl alkyl group. Nested within this family envelope is IPR005636 (DTW domain) from residues 65–293. The DTW domain is a soluble, globular module that typically forms oligomeric scaffolds and binds nucleic acids or acidic protein surfaces; here, its central placement and breadth indicate that RNA recognition and catalysis are co-localized within a single soluble core. The N-terminal segment preceding residue 24 likely contributes targeting or structural stabilization rather than membrane insertion, consistent with a soluble enzyme that associates with membranes peripherally.

2. 02

   This domain layout dictates molecular function.

   The YIPF3/TUT1 family signature (IPR051521) encodes chemistry that transfers an aminocarboxypropyl moiety from the donor S-adenosyl-L-methionine (SAM) onto uridine within structured RNA. The DTW catalytic scaffold provides the geometry to position uridine and the reactive aminocarboxypropyl group for acyl-alkyl transfer. This architecture causes a specific enzymatic activity: tRNA-uridine aminocarboxypropyltransferase activity, aligning with GO:0016765 transferase activity, transferring alkyl or aryl (other than methyl) groups and GO:0140101 catalytic activity, acting on a tRNA.

3. 03

   From function to process, installing an aminocarboxypropyl group on uridine constitutes a tRNA chemical maturation step that tunes decoding and stability.

   Such site-specific chemical elaborations are hallmarks of tRNA modification pathways, placing the enzyme squarely in GO:0006400 tRNA modification and GO:0008033 tRNA processing. The DTW-centered fold and soluble catalytic envelope support a role that precedes and coordinates with other maturation steps rather than acting as a terminal exonuclease or ligase.

4. 04

   Cellular location follows from the soluble architecture and the need to access nascent and nuclear-retained tRNAs.

   The absence of transmembrane segments and the presence of a soluble DTW core argue for a non-integral enzyme that can reversibly associate with membranes. This explains peripheral membrane association and supports a primary soluble pool in the nucleus, consistent with GO:0005634 nucleus and with observed nucleocytoplasmic dynamics. The experimentally observed cytoplasmic and membrane-proximal pools fit a model where the enzyme shuttles between nuclear tRNA biogenesis sites and cytoplasmic/peripheral membrane locales, using RNA and acidic membrane-protein interactions to localize catalysis.

5. 05

   Mechanistically, I hypothesize that the enzyme binds structured tRNA via the DTW domain, orients uridine within a conserved surface groove, and transfers the aminocarboxypropyl group using SAM as donor in a single-step alkyl transfer.

   The reaction likely proceeds through a transient polar intermediate stabilized by basic residues and looped RNA contacts that the DTW fold provides. As for interaction partners, a plausible network emerges: nuclear tRNA biogenesis and export factors (e.g., La/SSB and exportin-t complexes) would hand off substrates; nucleolar and nucleoplasmic RNA chaperones would assist folding; and peripheral membrane adaptors could transiently tether the enzyme near the nuclear envelope or ER surface where tRNA modification hubs concentrate. Together, these features define a soluble, membrane-tethered tRNA-modifying transferase that operates predominantly in the nucleus but can function at membrane-proximal sites to complete aminocarboxypropyl transfer chemistry.