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Researchers discovered that prokaryotic organisms and bacteriophages possess homologs of the major vault protein (MVP) that can self-assemble into vault-like nanocapsules, similar to those found in eukaryotic cells. Through screening approximately 15 billion proteins, they identified MVP homologs across 29 bacterial and 4 archaeal phyla, successfully expressed eight variants in E. coli, and determined high-resolution structures showing these prokaryotic vaults can be 25% larger than human vaults. The study demonstrates that vault size can be engineered by adding or removing wall repeats, with prokaryotic MVPs typically having seven repeats compared to nine in eukaryotic versions.
Why it matters
This discovery provides a simpler prokaryotic system for studying vault assembly and function, which has remained mysterious since vaults were discovered 40 years ago. The size-tunable nature of these vault nanocapsules offers potential applications in drug delivery, enzyme encapsulation, and nanotechnology, as they represent some of the largest defined protein shells known outside of virus capsids.
Understand the Science
⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Vaults are the largest ribonucleoprotein particles in eukaryotic cells, built from 78 copies of the major vault protein (MVP), yet their function remains unknown four decades after their discovery. MVP homologs occur in prokaryotes and bacteriophages, but whether they form vaults is unknown. Here, we show that prokaryotic and bacteriophage MVP homologs assemble into vault particles. We surveyed approximately 15 billion proteins, found MVP homologs in 29 bacterial and 4 archaeal phyla, and used size-exclusion chromatography to rapidly screen and isolate vault particles of eight homologs expressed in Escherichia coli. Cryo-electron microscopy structures of the phage homolog L05 at high resolution reveal a shell of 96 MVP chains enclosing a volume ~25% larger than human vaults, among the largest protein shells of defined size outside virus capsids. Prokaryotic MVPs typically carry seven wall repeats and eukaryotic MVPs nine, and adding wall repeats to L05 yields larger vaults. Prokaryotic vaults expand the known diversity of vault architecture and offer a tractable system for studying vault assembly and a size-tunable scaffold for cargo encapsulation.
Source: Prokaryotic homologs of the major vault protein form engineerable vault nanocapsules