biostudies-literatureUnknown7(42)Li SLon is an evolutionarily conserved proteolytic machine carrying out a wide spectrum of biological activities by degrading misfolded damaged proteins and specific cellular substrates. Lon contains a large N-terminal domain and forms a hexameric core of fused adenosine triphosphatase and protease domains. Here, we report two complete structures of Lon engaging a substrate, determined by cryo–electron microscopy to 2.4-angstrom resolution. These structures show a multilayered architecture featuring a tensegrity triangle complex, uniquely constructed by six long N-terminal helices. The interlocked helix triangle is assembled on the top of the hexameric core to spread a web of six globular substrate-binding domains. It serves as a multipurpose platform that controls the access of substrates to Science advanceseabj7835https://www.ebi.ac.uk/biostudies/studies/S-EPMC8519571biostudies-literatureComplete three-dimensional structures of the Lon protease translocating a protein substrate.PMC8519571Hsieh KYLi SZhang KLee SHPintilie GDChang CIKuo CIfalseComplete three-dimensional structures of the Lon protease translocating a protein substrate.Lon is an evolutionarily conserved proteolytic machine carrying out a wide spectrum of biological activities by degrading misfolded damaged proteins and specific cellular substrates. Lon contains a large N-terminal domain and forms a hexameric core of fused adenosine triphosphatase and protease domains. Here, we report two complete structures of Lon engaging a substrate, determined by cryo–electron microscopy to 2.4-angstrom resolution. These structures show a multilayered architecture featuring a tensegrity triangle complex, uniquely constructed by six long N-terminal helices. The interlocked helix triangle is assembled on the top of the hexameric core to spread a web of six globular substrate-binding domains. It serves as a multipurpose platform that controls the access of substrates to 2021-01-01T00:00:00Z2021 Oct2026-05-08T15:50:36.303Z2025-02-19T00:03:16.983ZS-EPMC85195713465294710.1126/sciadv.abj7835