| Aspect | Key evidence/statement | Key sources with year and DOI URL |
|---|---|---|
| Identity | Human **EMC1** matches UniProt **Q8N766** as **ER membrane protein complex subunit 1**, a core subunit of the conserved ER membrane protein complex (EMC) involved in membrane protein biogenesis; EMC1 is a large luminal/transmembrane structural subunit rather than an enzyme or transporter itself. (pqac-00000003, pqac-00000006) | Hegde 2022, *Annu Rev Biochem*, https://doi.org/10.1146/annurev-biochem-032620-104553; Alzayed et al. 2024, *Neurol Genet*, https://doi.org/10.1212/NXG.0000000000200156 |
| Localization | EMC resides in the **endoplasmic reticulum membrane** with tripartite organization (ER lumen, membrane, cytosol); EMC1 is predominantly **luminal**, contributes a **transmembrane helix**, and helps form/stabilize the transmembrane region. Human EMC also forms a **VDAC-associated state at mitochondria-ER contact sites**. (pqac-00000001, pqac-00000010) | Bai et al. 2020, *Nature*, https://doi.org/10.1038/s41586-020-2389-3; Li et al. 2024, *Aging (Albany NY)*, https://doi.org/10.18632/aging.205660 |
| Molecular function | Primary function is **structural and chaperone/insertase support** within EMC: EMC catalyzes or facilitates **energy-independent insertion of low-hydrophobicity transmembrane helices** and supports folding/assembly of multipass and some tail-anchored membrane proteins; EMC1 contributes to client handling beyond the core insertase pocket. (pqac-00000003, pqac-00000004, pqac-00000005) | Alzayed et al. 2024, *Neurol Genet*, https://doi.org/10.1212/NXG.0000000000200156; Hegde 2022, *Annu Rev Biochem*, https://doi.org/10.1146/annurev-biochem-032620-104553; Pleiner et al. 2023, *J Cell Biol*, https://doi.org/10.1083/jcb.202212007 |
| Mechanism | EMC captures client TMDs via **cytosolic methionine-rich loops** and inserts them through a **hydrophilic vestibule**; positive charges at the vestibule entrance act as a **selectivity filter** that excludes many mitochondrial TA proteins and enforces the **positive-inside rule** for topology. EMC1 luminal regions and TM-associated surfaces also participate in client-specific chaperoning/holdase functions. (pqac-00000005, pqac-00000012, pqac-00000014) | Pleiner et al. 2023, *J Cell Biol*, https://doi.org/10.1083/jcb.202212007; Chen et al. 2023, *Nature*, https://doi.org/10.1038/s41586-023-06175-5 |
| EMC1-specific mechanism | In the CaV assembly intermediate, **EMC1 forms part of the TM dock/brace-crossbar system** that binds CaV1.2 VSD I; EMC1 residues including **Asp961** and **Arg981** contribute to client interaction, and client binding shifts the EMC1 luminal brace/crossbar helix into an **up conformation**, consistent with a client-loaded holdase state. (pqac-00000012, pqac-00000014) | Chen et al. 2023, *Nature*, https://doi.org/10.1038/s41586-023-06175-5 |
| Client/substrate examples | EMC-dependent proteins are enriched for **multipass transporters/ion channels** containing **polar/charged TMD residues**. Examples discussed experimentally include **FDFT1/SQS**, **ZFPL1**, **CD9**, **ERGIC3** (engineered to become EMC-dependent), **SEC61A1** (engineered EMC dependence), and EMC-supported ion channel assembly such as **CaV1.2**. (pqac-00000015, pqac-00000016, pqac-00000013) | Tian et al. 2019, *Cell Rep*, https://doi.org/10.1016/j.celrep.2019.08.006; Chen et al. 2023, *Nature*, https://doi.org/10.1038/s41586-023-06175-5 |
| Structural insights 2023 | A 2023 cryo-EM study provided the first direct **EMC-client complex** for a mammalian ion channel assembly intermediate: EMC binds **CaV1.2–CaVβ3**, partially extracts pore elements, and is **mutually exclusive with CaVα2δ**, supporting a **handoff model** during channel assembly. (pqac-00000013, pqac-00000014) | Chen et al. 2023, *Nature*, https://doi.org/10.1038/s41586-023-06175-5 |
| Structural insights 2024 | Human EMC cryo-EM structures in **apo** and **VDAC-bound** states at **3.47 Å** and **3.32 Å** identified an **EMC3 gating plug** in the hydrophilic vestibule; conformational changes suggest the VDAC-bound state is unlikely to be actively inserting clients and may represent another EMC functional mode at ER-mitochondria contacts. (pqac-00000010, pqac-00000017) | Li et al. 2024, *Aging (Albany NY)*, https://doi.org/10.18632/aging.205660 |
| Structural architecture relevant to EMC1 | EMC1 contains a large luminal domain including an **eight-bladed WD/β-propeller-like fold**; in human EMC, a second β-propeller has been noted in review literature. EMC1 also contains a membrane-proximal/brace helix and contributes one TM helix to the complex architecture. (pqac-00000001, pqac-00000006) | Bai et al. 2020, *Nature*, https://doi.org/10.1038/s41586-020-2389-3; Hegde 2022, *Annu Rev Biochem*, https://doi.org/10.1146/annurev-biochem-032620-104553 |
| Disease genetics/phenotypes | Pathogenic human **EMC1** variants cause **CAVIPMR** (cerebellar atrophy, visual impairment, psychomotor retardation) and related neurodevelopmental phenotypes. In a 2024 Kuwaiti founder-variant series (**p.Thr82Met**), major features were **global developmental delay 8/8**, **microcephaly 8/8**, **truncal hypotonia 8/8**, **visual impairment 7/7**, **failure to thrive 7/7**, **epilepsy 4/8**, **chorea 3/8**, **cerebellar atrophy 4/7**, **cerebral atrophy 3/6**. (pqac-00000003) | Alzayed et al. 2024, *Neurol Genet*, https://doi.org/10.1212/NXG.0000000000200156 |
| Disease relevance to retinal biology | Reviews of inherited retinal vascular disease note **EMC1** among newer genes linked to **FEVR-like retinal phenotypes**, likely through effects on ER biogenesis of transmembrane proteins rather than as a canonical Norrin-pathway signaling protein itself. (pqac-00000008, pqac-00000009) | Le et al. 2023, *Cells*, https://doi.org/10.3390/cells12212579 |
| Quantitative stats | Yeast EMC cryo-EM map reached **3.0 Å** and the complex measured about **160 × 100 × 80 Å**; human EMC apo and VDAC-bound structures were solved at **3.47 Å** and **3.32 Å**; Tian et al. identified **36 EMC-dependent** and **171 EMC-independent** transmembrane proteins under stringent criteria; Klose et al. later reported **506 enriched interactors**, including **>200 transmembrane proteins**. (pqac-00000001, pqac-00000010, pqac-00000015, pqac-00000000) | Bai et al. 2020, *Nature*, https://doi.org/10.1038/s41586-020-2389-3; Li et al. 2024, *Aging (Albany NY)*, https://doi.org/10.18632/aging.205660; Tian et al. 2019, *Cell Rep*, https://doi.org/10.1016/j.celrep.2019.08.006; Klose et al. 2025, *Nat Commun*, https://doi.org/10.1038/s41467-025-62109-x |
| Functional interpretation for annotation | Best-supported annotation for human EMC1: **ER-resident luminal/transmembrane scaffold and client-engagement subunit of the EMC**, required for **biogenesis, topology control, folding, and assembly of challenging membrane proteins**, especially those with **low-hydrophobicity or polar TMDs**; disease likely arises from impaired proteostasis of critical client proteins in nervous system and eye. (pqac-00000004, pqac-00000005, pqac-00000012, pqac-00000003) | Hegde 2022, *Annu Rev Biochem*, https://doi.org/10.1146/annurev-biochem-032620-104553; Pleiner et al. 2023, *J Cell Biol*, https://doi.org/10.1083/jcb.202212007; Chen et al. 2023, *Nature*, https://doi.org/10.1038/s41586-023-06175-5; Alzayed et al. 2024, *Neurol Genet*, https://doi.org/10.1212/NXG.0000000000200156 |


*Table: This table summarizes verified identity, localization, function, mechanism, structural biology, client examples, and disease evidence for human EMC1 (UniProt Q8N766). It is designed as a concise functional-annotation aid with direct source links and context-ID citations.*