# The Vault (DD-015)

> Vaults are giant, hollow, barrel-shaped particles made of protein and RNA. They're found in the cytoplasm of most eukaryotic cells, with about 10,000 in a typical human cell. Each one is a 12.9-megadalton shell made of 78 copies of the major vault protein, built as two identical 39-protein halves. It also carries smaller partners (VPARP, TEP1 and vault RNA). Nearly 40 years after their discovery in 1986, nobody knows for sure what vaults do.

- Department: Science (also Nature)
- First published: 2026-08-05
- Last updated: 2026-08-05
- Permalink: https://detailenjoyer.com/case/the-vault/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## On the timeline

- **1986**: UCLA's Nancy Kedersha and Leonard Rome discover vaults in rat-liver cells

Full timeline: https://detailenjoyer.com/timeline/?case=the-vault

## Quick facts

- **DD-015-F01**: Vaults are hollow, barrel-shaped particles in most of our cells (about 10,000 per cell), each built from 78 copies of one protein, and nobody knows for sure what they do. _(Write-up · Exhibit B (Big and everywhere))_
- **DD-015-F02**: A vault weighs about 12.9 megadaltons and is made of two identical halves of 39 major vault proteins each. _(Write-up · Exhibit C (One protein does most of the work))_

## Write-up

Your cells are full of hollow barrels called vaults. Each one is built from 78 copies of a single protein.

1. **Found by accident in 1986**: UCLA's Nancy Kedersha and Leonard Rome found vaults in 1986 while trying to purify coated vesicles from rat liver. Under the microscope the particles looked like the arches of a cathedral's vaulted ceiling, which gave them their name.
2. **Big and everywhere**: Vaults measure about 35 × 65 nm, much larger than ribosomes. Most human cells hold roughly 10,000 of them, and some immune cells may have up to 100,000.
3. **One protein does most of the work**: The shell is made of the ~100 kDa major vault protein (MVP). Vaults also carry two minor proteins, VPARP (vault poly(ADP-ribose) polymerase, 193 kDa) and TEP1 (telomerase-associated protein 1), plus small vault RNAs.
4. **12.9 megadaltons**: Vaults have a molecular mass of about 12.9 MDa. Measured at roughly 670 Å long and 400 Å wide, the hollow interior is big enough to hold most objects found in a cell.
5. **78 copies in two halves**: The X-ray structure (3.5 Å) shows the shell is 78 MVP molecules. Two identical halves of 39 MVPs each join at the 'waist', giving the particle 39-fold dihedral (D39) symmetry.
6. **Paper-thin walls, protruding caps**: The barrel wall is only about 15–25 Å thick. Each end has a protruding cap, formed by MVP's own cap-helix and cap-ring domains. The 39-fold symmetry breaks in that cap region.
7. **Still a mystery**: Despite decades of work, the vault's function is unknown. Proposed roles include intracellular transport, signalling, immunity and drug resistance, and researchers are now engineering synthetic vaults to deliver therapies.

## Related case files

- [Macrophagia (DD-044)](https://detailenjoyer.com/case/macrophagia/): Another case about what goes on inside a cell.

## Reel vs. record

- **Incomplete**: the component list leaves out TEP1 (telomerase-associated protein 1), the second minor vault protein alongside VPARP. Mammalian vaults contain MVP, VPARP, TEP1 and vault RNA. [Kato et al. 2008; SPring-8; van Zon et al. 2003]
- **Imprecise**: 'flexible "cap" proteins'. The caps aren't separate proteins. They're the cap-helix and cap-ring domains at the end of each MVP molecule. The cap region is dynamic, and the 39-fold symmetry breaks there. [SPring-8; RCSB 4HL8]
- **Minor**: 12.9 MDa is the classic STEM measurement. Some structural papers round to 'about 10 MDa' for the protein shell. [Kato et al. 2008; RCSB 4HL8]

## Video: The Vault: Your Cells Are Full of Hollow Barrels Called Vaults

- Duration: 32.3 s · Published: 2026-08-05
- File: https://detailenjoyer.com/assets/videos/DbrgDXyxibQ.mp4

### Transcript

DID YOU KNOW? Vaults are enormous ribonucleoprotein particles found in the cytoplasm of most eukaryotic cells, built primarily from major vault protein, MVP, and smaller components including vault RNA and the vault poly(ADP-ribose) polymerase proteins. Each vault resembles a hollow barrel or inverted cathedral vault and has a molecular mass of roughly 12.9 megadaltons. The particles are assembled from two identical halves, each containing 39 copies of MVP arranged into a symmetrical structure, with a central cavity and flexible "cap" proteins. NOW YOU KNOW!

## Questions & answers

**Q: Why are vaults called 'vaults'?**  
A: Kedersha and Rome named them for their resemblance to the multiple arches of cathedral vaults. _(Source: Write-up · Exhibit A (Found by accident in 1986) · Isolation and characterization of a novel ribonucleoprotein particle (Kedersha & Rome, J. Cell Biol. 1986); The key to 'the vault' (California NanoSystems Institute, UCLA, May 27, 2024))_

**Q: Roughly how many vaults does a typical human cell contain?**  
A: Most human cells have around 10,000 vaults; some immune cells may have up to 100,000. _(Source: Write-up · Exhibit B (Big and everywhere) · Isolation and characterization of a novel ribonucleoprotein particle (Kedersha & Rome, J. Cell Biol. 1986); The vault complex (van Zon et al., Cell Mol Life Sci 2003, via PMC); How a scientist's lifelong obsession with vaults could transform medicine (UCLA Health))_

**Q: How many copies of the major vault protein (MVP) make up one vault shell?**  
A: 78 MVPs, in two identical halves of 39 each. _(Source: Write-up · Exhibit E (78 copies in two halves) · Structure of Rat Liver Vault at 3.5 Å Resolution (SPring-8 Research Frontiers 2009); RCSB PDB 4HL8: Re-refinement of the vault ribonucleoprotein particle; A vault ribonucleoprotein particle exhibiting 39-fold dihedral symmetry (Kato et al., Acta Cryst D 2008))_

**Q: What is a vault's approximate molecular mass?**  
A: Vaults are about 12.9 MDa, among the largest particles cells make. _(Source: Write-up · Exhibit D (12.9 megadaltons) · A vault ribonucleoprotein particle exhibiting 39-fold dihedral symmetry (Kato et al., Acta Cryst D 2008); Structure of Rat Liver Vault at 3.5 Å Resolution (SPring-8 Research Frontiers 2009))_

**Q: What is the known function of vaults?**  
A: Nearly 40 years after their discovery, the vault's function remains unknown. _(Source: Write-up · Exhibit G (Still a mystery) · How a scientist's lifelong obsession with vaults could transform medicine (UCLA Health); The vault complex (van Zon et al., Cell Mol Life Sci 2003, via PMC); The key to 'the vault' (California NanoSystems Institute, UCLA, May 27, 2024))_

## Sources

- [Isolation and characterization of a novel ribonucleoprotein particle (Kedersha & Rome, J. Cell Biol. 1986)](https://doi.org/10.1083/jcb.103.3.699)
- [The vault complex (van Zon et al., Cell Mol Life Sci 2003, via PMC)](https://pmc.ncbi.nlm.nih.gov/articles/PMC11138885/)
- [A vault ribonucleoprotein particle exhibiting 39-fold dihedral symmetry (Kato et al., Acta Cryst D 2008)](https://doi.org/10.1107/s0907444908004277)
- [Structure of Rat Liver Vault at 3.5 Å Resolution (SPring-8 Research Frontiers 2009)](https://spring8.jp/archive/pdf/en/res_fro/09/028-029.pdf)
- [RCSB PDB 4HL8: Re-refinement of the vault ribonucleoprotein particle](https://www.rcsb.org/structure/4HL8)
- [How a scientist's lifelong obsession with vaults could transform medicine (UCLA Health)](https://www.uclahealth.org/news/publication/how-scientists-lifelong-obsession-with-vaults-could)
- [The key to 'the vault' (California NanoSystems Institute, UCLA, May 27, 2024)](https://cnsi.ucla.edu/may-27-2024-the-key-to-the-vault/)

## Cite this case file

Easterling, Marcus. "The Vault." The Detail Department (DetailEnjoyer), case file DD-015, last updated Aug 5, 2026. https://detailenjoyer.com/case/the-vault/