Vault particles are enormous, hollow protein shells found in many eukaryotic cells, but their biological role remains unknown. Researchers identified related proteins in bacteria, archaea, and bacteriophages and tested whether they could form vault-like structures. The proteins are rare - found in 29 bacterial groups and four archaeal groups, but in fewer than 1% of sequenced species. Using Claude to search protein databases and help design experiments, the team produced and isolated a vault made from a bacteriophage protein inside bacteria. Its existence offers a simpler system for studying vaults than mammalian cells, though it does not yet explain what they do.
Cryo-electron microscopy revealed a particle assembled from 96 copies of one protein, with a mass of about 9.5 megadaltons. It is shorter and wider than the mammalian vault, encloses more volume, and closes with a stepped cap formed by protein chains taking different shapes. Altering cap-region residues left some particles open, showing those regions help seal the shell. Adding two repeated segments to each protein produced an even larger vault, supporting the idea that duplication could change vault size without disrupting assembly. Claude assisted with sequence searches, DNA designs, purification, and microscopy analysis; the team reduced isolation from about three days to 90 minutes and obtained an initial structural model in 34 hours, rather than weeks. The findings also suggest possible use of vaults as engineered nanocapsules, while their natural function remains unresolved.
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