GON7

Model summary

A small, soluble adaptor subunit of the human KEOPS assembly that organizes and stabilizes the complex responsible for installing the threonylcarbamoyladenosine modification at position 37 of ANN-decoding tRNAs. By mediating multivalent protein contacts, it maintains the integrity and localization of the complex across cytosol and nucleoplasm, with enrichment in nucleolar RNA-processing hubs. This scaffolding role supports efficient tRNA modification by positioning catalytic and adaptor modules and coordinating with RNA maturation pathways.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture: IPR027893 (EKC/KEOPS complex subunit GON7, metazoa family) spans residues 1–100, covering essentially the entire polypeptide.

   A single, full-length family signature without catalytic subdomains indicates a small, non-enzymatic subunit that stabilizes and organizes a larger macromolecular assembly rather than performing chemistry itself. This architecture causally points to a role as a structural adaptor that mediates multivalent contacts within a complex, which directly supports GO:0005515 protein binding as the primary molecular function.

2. 02

   From this scaffold-like nature, I infer the biological role by examining the complex this subunit builds.

   The KEOPS/EKC assembly catalyzes formation of threonylcarbamoyladenosine (t6A) at position 37 of ANN-decoding tRNAs. Although this subunit is non-catalytic, its presence is necessary to assemble and maintain the active KEOPS architecture that executes GO:0002949 tRNA threonylcarbamoyladenosine modification. The causal chain is: a full-length adaptor domain enforces complex integrity; the intact complex positions the catalytic core; the modification proceeds efficiently on target tRNAs.

3. 03

   Cellular localization follows from where tRNA maturation and KEOPS function occur.

   The absence of transmembrane features and the adaptor role argue for soluble compartments. KEOPS operates in both cytoplasmic and nuclear pathways of RNA metabolism; thus I localize it to GO:0005829 cytosol and GO:0005654 nucleoplasm. KEOPS and associated RNA-processing factors frequently concentrate in the GO:0005730 nucleolus, consistent with ribonucleoprotein assembly and RNA surveillance. The explicit complex membership is captured by GO:0000408 EKC/KEOPS complex.

4. 04

   Mechanistically, this subunit likely stabilizes the KEOPS assembly that uses ATP-driven conformational cycles to achieve t6A formation.

   By providing a rigidifying interface, it promotes correct positioning of the catalytic subunit and accessory ATPase/adaptor modules, thereby tuning assembly/disassembly and substrate channeling. I hypothesize that it binds other KEOPS constituents—particularly the catalytic and adaptor subunits—to nucleate a stable platform that recognizes and modifies tRNA(A37). In this model, transient interactions with RNA-binding and ATP-handling partners in the cytosol and nucleoplasm coordinate modification with broader RNA biogenesis, with nucleolar enrichment reflecting coupling to tRNA and ribonucleoprotein maturation hubs.