IFIT1B

Model summary

A cytosolic helical-repeat scaffold that uses multiple tetratricopeptide motifs to assemble and tune antiviral and interferon-responsive complexes. By forming a high-avidity binding platform, it captures and allosterically restrains RNA helicase and ATP-dependent assemblies, thereby exerting context-dependent control over viral genome replication. It operates primarily in the cytosol but is recruited to actin-rich membrane ruffles and apical domains where innate immune signaling and trafficking concentrate, coordinating innate and type I interferon pathways through multivalent protein binding and sequestration mechanisms.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The polypeptide is dominated by IPR011990 (Tetratricopeptide-like helical domain superfamily, residues 2–468), a solenoidal helical scaffold that typically forms extended superhelices for multivalent protein–protein interactions. Within this scaffold lie multiple discrete TPR units: IPR019734 TPR repeats at residues 52–85, 95–128, 141–174, 251–284, 340–373, and 437–470. The ordered placement of several TPR motifs across the length of the protein creates a continuous binding surface that stabilizes transient assemblies rather than catalyzing chemistry. This architecture causally enforces a molecular function centered on multivalent protein binding, aligning with GO:0005515 protein binding.

2. 02

   A TPR-based scaffold of this kind is well-suited to regulate macromolecular machines by competitive binding and allosteric control.

   In the innate immune pathway, such scaffolds can sequester or remodel viral replication assemblies and host sensors. The observed biological processes cohere around antiviral and interferon pathways: GO:0045087 innate immune response and GO:0071357 cellular response to type I interferon describe the signaling milieu in which this scaffold operates. Its presence in GO:0071360 cellular response to exogenous dsRNA is consistent with sensing and buffering dsRNA-triggered cascades. The bidirectional control of viral replication—GO:0045070 positive regulation of viral genome replication and GO:0045071 negative regulation of viral genome replication—follows directly from a scaffold that can either stabilize replication complexes or disrupt them, depending on partner occupancy and phosphorylation state.

3. 03

   The TPR platform also explains modulation of host ATP-dependent enzymes and RNA helicases.

   GO:0032780 negative regulation of ATP-dependent activity and GO:0051095 regulation of helicase activity arise when the scaffold binds and inhibits viral or cellular helicases, thereby tuning RNA remodeling and translation. GO:0032091 negative regulation of protein binding can be produced by high-avidity TPR-mediated capture that outcompetes other partners. GO:0015031 protein transport is rationalized by the scaffold’s role in assembling and positioning complexes that traffic between cytosol and membrane-associated structures.

4. 04

   Cellular localization follows from the same architecture and processes.

   The soluble, helical-repeat scaffold supports cytosolic residence (GO:0005829 cytosol). Its participation in actin-rich zones and membrane-proximal assemblies accounts for GO:0015629 actin cytoskeleton and GO:0032587 ruffle membrane, consistent with transient recruitment to dynamic cortical structures. Association with kinase assemblies is captured by GO:1902554 serine/threonine protein kinase complex, reflecting proximity to interferon- and stress-activated kinase modules. Polarized epithelial contexts explain GO:0045177 apical part of cell, where interferon and antiviral signaling often concentrate.

5. 05

   Mechanistically, the TPR array forms a high-affinity hub that binds and inhibits viral RNA helicase machinery and interferon-responsive complexes.

   By occupying critical binding grooves on viral replicase assemblies, it can both sequester and stabilize them, producing context-dependent positive or negative effects on genome replication. In parallel, it dampens ATP-dependent activities and helicase-driven RNA remodeling by competitive binding and allosteric restraint. This same binding logic extends to innate immune signaling nodes and cytoskeletal adaptors, positioning the protein as a cytosolic, membrane-proximal regulator that tunes antiviral responses and trafficking routes.

6. 06

   From these features, I hypothesize interactions with interferon-induced antiviral assemblies and RNA helicase systems.

   Likely partners include the mitochondrial antiviral signaling axis and its cytosolic adaptors, as well as cytosolic RNA helicases and their cofactors. The scaffold’s TPR repeats would capture these targets to modulate their assembly, localization, and activity in the cytosol and at actin-rich membrane ruffles.