Abstact

The vault protein is expressed in most eukaryotic cells, where it is assembled on polyribosomes into large hollow barrel-shaped complexes. Despite its widespread and abundant presence in cells, the biological function of the vault remains unclear. In this study, we describe the cryo-EM structure of vault particles that were imaged as a contamination of a preparation to extract tau filaments from brain tissue of an individual with progressive supranuclear palsy (PSP). We identify a mechanism of symmetry mismatch at the caps of the vault, from 39-fold to 13-fold symmetry, where two out of three monomers are sequentially excluded from the cap, resulting in a narrow, greasy pore at the tip of the vault. Our structure offers valuable insights for engineering carboxy-terminal modifications of the major vault protein (MVP) for potential therapeutic applications.