{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"702db1102bf43fa654684ea4cf84486af54c3c6dee3f016208bf7d4ae935ca7c","created":"2026-10-03T07:17:57Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"ae7960b72f5c64bc0b963178506a4f932d4baf04081ca9c83a00ba969bef392f","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"bio.chromatin-extrusion.motor-mechanism","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"Cohesin and condensin are ring-shaped protein machines that pull DNA into loops by burning ATP. Single-molecule experiments show steps of hundreds of base pairs, comparable to the size of the protein, and how the structure achieves this is unknown.","posed_since":"","precise":"Determine the conformational cycle of cohesin or condensin that couples ATP binding and hydrolysis to DNA translocation, explaining the measured step-size distribution (of order hundreds of base pairs per step, approximate), the force-velocity relation with stall at DNA tensions of order $10^{-8}\\text{ to }10^{-7}\\,\\mathrm{dyn}$ depending on the complex (approximate), and one-sided versus two-sided extrusion. Answer: a structural-kinetic model that reproduces these measurements.","problem_ref":null,"references":"","settled_by":"Time-resolved structures or single-molecule FRET of the motor cycle combined with force spectroscopy that match one model's predicted step and force-velocity statistics.","status_note":"Cryo-EM structures constrain the cycle, but several competing translocation models remain in 2026, to this survey's knowledge.","title":"Stepping mechanism of SMC loop-extruding motors","topic_ref":"8ad1a941274484056fe235f47000030ee6a6486f2d2e01d87c8ec53a250ea12e"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"d9d6f4da2bb7514c4cefb76b385fdb7e95db134545add3ad860b3640c35a1254","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"7fd8e61fec0b298f2ac855810981d7725ac5a7d84f5de8da6b5540e4828a7d33","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"lzt7M43WMws8UlPYMSMVv9CBilJK2hUR9cmrDjxNwjwLmywi0-i3tdRnBYyUFJ-wki_QdwxQ8XyzkAEgKkNaBA"},"schema":"pubphys.envelope/1"},"record_hash":"d9d6f4da2bb7514c4cefb76b385fdb7e95db134545add3ad860b3640c35a1254","leaf_index":743}