Affinage

TOMT

Transmembrane O-methyltransferase · UniProt Q8WZ04

Length
291 aa
Mass
32.2 kDa
Annotated
2026-04-28
13 papers in source corpus 4 papers cited in narrative 4 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

TOMT (LRTOMT2 in humans; also called COMT2 in mice) is an inner-ear hair-cell protein that, despite possessing catechol-O-methyltransferase activity, functions independently of its enzymatic activity to traffic the mechanotransduction channel subunits TMC1 and TMC2 from the Golgi through the secretory pathway into stereocilia, thereby enabling assembly of a functional mechanotransduction complex (PMID:28534737, PMID:28504928). TOMT directly binds TMC1 via an interaction modulated by His183, and its loss selectively excludes TMC1/2 from the hair bundle while leaving other mechanotransduction complex components correctly localized, abolishing mechanotransduction currents (PMID:28534737, PMID:28504928). Mutations in the human ortholog LRTOMT—a primate-specific fusion gene encoding LRTOMT2—cause profound nonsyndromic sensorineural deafness DFNB63 (PMID:18953341, PMID:18794526).

Mechanistic history

Synthesis pass · year-by-year structured walk · 2 steps
  1. 2008 High

    Identification of TOMT/LRTOMT as a deafness gene established that a catechol-O-methyltransferase–domain protein is required for auditory and vestibular function, and that the human gene arose from a primate-lineage fusion of two ancestral loci (Lrrc51 and Tomt).

    Evidence Positional cloning of DFNB63 families and of a chemically induced mouse mutant, combined with enzymatic activity assays and comparative genomics

    PMID:18794526 PMID:18953341

    Open questions at the time
    • Whether the methyltransferase activity itself is the functionally relevant mechanism was not resolved
    • The specific molecular partners of TOMT in hair cells were unknown
    • Subcellular site of TOMT action in hair cells was not determined
  2. 2017 High

    Two independent studies resolved the mechanism: TOMT localizes to the Golgi, directly binds TMC1/2, and acts as a trafficking chaperone that delivers TMC proteins to stereocilia—independently of methyltransferase catalytic activity—thereby enabling mechanotransduction channel function.

    Evidence Zebrafish loss-of-function and conditional knockout mouse models combined with live-cell GFP imaging, co-immunoprecipitation in HEK 293 cells, site-directed mutagenesis of His183, electrophysiology of mechanotransduction currents, and rescue experiments with catalytically inactive TOMT versus COMT

    PMID:28504928 PMID:28534737

    Open questions at the time
    • Structural basis of the TOMT–TMC interaction and the role of His183 remain undefined
    • Whether TOMT traffics additional cargo beyond TMC1/2 is unknown
    • The mechanism by which TOMT selectively recognizes TMC proteins over other stereocilia proteins has not been determined

Open questions

Synthesis pass · forward-looking unresolved questions
  • It remains unresolved how TOMT distinguishes TMC1/2 from other membrane proteins in the secretory pathway, what structural features mediate the interaction, and whether TOMT serves additional roles in the hair cell beyond TMC trafficking.
  • No structural model of the TOMT–TMC complex exists
  • Post-Golgi trafficking route from TOMT handoff to stereocilia insertion is uncharacterized
  • Potential non-hair-cell functions of TOMT have not been investigated

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0044183 protein folding chaperone 2 GO:0016740 transferase activity 1
Localization
GO:0005794 Golgi apparatus 1
Pathway
R-HSA-9709957 Sensory Perception 2
Partners
TMC1TMC2

Evidence

Reading pass · 4 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2008 LRTOMT encodes two proteins via alternative reading frames: LRTOMT1 and LRTOMT2 (a putative methyltransferase), and mutations in LRTOMT cause profound nonsyndromic hearing loss (DFNB63). In the primate lineage, LRTOMT evolved from the fusion of two ancestral genes (Lrrc51 and Tomt) that exist as separate genes in rodents. Positional cloning, protein blot analysis, comparative genomics Nature genetics High 18953341
2008 TOMT (designated COMT2 in mice) encodes a catechol-O-methyltransferase expressed in sensory hair cells of the inner ear; a missense mutation significantly reduces COMT2 enzymatic activity and causes vestibular impairment, profound sensorineural deafness, and progressive degeneration of the organ of Corti in mice, and a human nonsense mutation in its ortholog causes nonsyndromic deafness. Positional cloning of chemically induced mutation, enzymatic activity assay, human genetic screening Proceedings of the National Academy of Sciences of the United States of America High 18794526
2017 TOMT is essential for mechanotransduction (MET) in hair cells; in tomt-deficient zebrafish, Tmc1/2 proteins are specifically excluded from the hair bundle while other MET complex proteins localize normally. GFP-tagged Tomt is enriched in the Golgi, and mouse TOMT and TMC1 directly interact in HEK 293 cells, with interaction modulated by His183 in TOMT, indicating TOMT traffics TMC proteins through the secretory pathway to the hair bundle. Zebrafish loss-of-function model, live-cell fluorescence imaging (GFP-Tomt), co-immunoprecipitation in HEK 293 cells, site-directed mutagenesis (His183), electrophysiology (MET recording) eLife High 28534737
2017 mTOMT (murine TOMT/COMT2) is essential for mechanotransduction in cochlear hair cells through a mechanism independent of its methyltransferase activity; mCOMT cannot substitute for mTOMT function. mTOMT binds putative mechanotransduction channel components and is required for their transport into stereocilia, indicating functional diversification between mCOMT and mTOMT. Conditional knockout mouse, electrophysiology (mechanotransduction currents), co-immunoprecipitation, methyltransferase activity assays with rescue experiments eLife High 28504928

Source papers

Stage 0 corpus · 13 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2016 Lignin biosynthesis in wheat (Triticum aestivum L.): its response to waterlogging and association with hormonal levels. BMC plant biology 70 26811086
2008 Mutations of LRTOMT, a fusion gene with alternative reading frames, cause nonsyndromic deafness in humans. Nature genetics 56 18953341
2008 A catechol-O-methyltransferase that is essential for auditory function in mice and humans. Proceedings of the National Academy of Sciences of the United States of America 53 18794526
2017 Integration of Tmc1/2 into the mechanotransduction complex in zebrafish hair cells is regulated by Transmembrane O-methyltransferase (Tomt). eLife 50 28534737
2017 The murine catecholamine methyltransferase mTOMT is essential for mechanotransduction by cochlear hair cells. eLife 29 28504928
2016 RNAi downregulation of three key lignin genes in sugarcane improves glucose release without reduction in sugar production. Biotechnology for biofuels 26 28031745
2020 Genotoxic effects and proteomic analysis on Allium cepa var. agrogarum L. root cells under Pb stress. Ecotoxicology (London, England) 14 32507983
2011 Transcript Accumulation Dynamics of Phenylpropanoid Pathway Genes in the Maturing Xylem and Phloem of Picea abies during Latewood Formation. Journal of integrative plant biology 6 21767344
2019 Catechol O-methyltransferase homologs in Schizosaccharomyces pombe are response factors to alkaline and salt stress. Applied microbiology and biotechnology 4 31053915
2025 Integrated Metabolome, Transcriptome, and Physiological Analysis of the Flavonoid and Phenylethanol Glycosides Accumulation in Wild Phlomoides rotata Roots from Different Habitats. International journal of molecular sciences 1 39859384
2025 The Fiber Cell-Specific Overexpression of COMT2 Modulates Secondary Cell Wall Biosynthesis in Poplar. Plants (Basel, Switzerland) 1 40573727
2019 Effects of field-grown transgenic switchgrass carbon inputs on soil organic carbon cycling. PeerJ 1 31637134
2023 Evaluation of Comt2, Comt3, Cyp1b1, and Esr1 gene polymorphisms as risk factor for endometrial polyp. Women & health 0 37908103