TOMM40L

Model summary

A β-barrel channel of the mitochondrial outer membrane that forms the core pore of the outer membrane translocase. It assembles a high-capacity conduit for precursor proteins, using multivalent protein interactions to receive cargo from cytosolic receptors and hand it off to downstream pathways. By scaffolding receptor and assembly factors, it drives insertion of proteins into the outer membrane and operates as a membrane-embedded hub within a larger import complex.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   IPR037930 (Tom40 family, residues 21–308) and IPR027246 (Eukaryotic porin/Tom40 family, residues 26–302) together define a eukaryotic β-barrel porin that forms the central pore of the mitochondrial outer membrane translocase. This barrel identity is reinforced by IPR023614 (Porin domain superfamily, residues 193–308), which marks the C-terminal half where the β-strands assemble into the canonical porin barrel. The ordered layout—an N-terminal Tom40-family core extending into a C-terminal porin superfamily module—causes formation of a large aqueous channel through the outer membrane. Such β-barrel porins are non-enzymatic and operate by selective translocation and gating through multivalent contacts with other proteins, which mechanistically supports GO:0005515 protein binding as the operative molecular function.

2. 02

   A β-barrel channel specialized by the Tom40 family architecture dictates a role in outer membrane translocation.

   By providing a conduit and docking platform for precursor proteins and assembly factors, this barrel drives the pathway formalized as GO:0045040 protein insertion into mitochondrial outer membrane. The barrel’s assembly into a higher-order translocase necessitates multimeric coordination with receptor and assembly modules; this reliance on macromolecular assembly situates the protein within GO:0032991 protein-containing complex. The porin/Tom40 signatures specify that the complex is the mitochondrial outer membrane translocase, where the barrel acts as the central pore and scaffold for receptor-guided import.

3. 03

   The β-barrel porin architecture inherently embeds the protein in the mitochondrial outer membrane.

   The absence of soluble domains and the presence of a membrane-embedded barrel infer a membrane-resident location, consistent with a multi-pass outer membrane topology in eukaryotes. This membrane-anchored state explains how the channel captures cytosol-derived precursors and funnels them across the outer membrane into downstream pathways.

4. 04

   Mechanistically, the barrel forms the central conduit of the TOM machinery and recruits receptor and assembly partners to choreograph precursor handover.

   I hypothesize that it binds TOM20 and TOM22 to receive hydrophobic precursors, engages TOM6 and TOM7 to regulate pore assembly and stability, and couples to ATOM/TOM5 and the SAM complex to finalize membrane insertion. Cytosolic chaperones likely transiently dock via receptor modules to deliver unfolded precursors through the pore. Together, these interactions produce a gated, high-capacity import channel that nucleates outer membrane biogenesis and import.