Transmembrane segments form tertiary hairpins in the folding vestibule of the ribosome.

摘要: Abstract Folding of membrane proteins begins in the ribosome as peptide is elongated. During this process, nascent navigates along 100 A tunnel from peptidyltransferase center to exit port. Proximal port a “folding vestibule” that permits compact and explore conformational space for potential tertiary folding partners. The latter occurs cytosolic subdomains but has not yet been shown transmembrane segments. We now demonstrate, using an accessibility assay improved intramolecular crosslinking assay, helical S3b–S4 hairpin (“paddle”) voltage-gated potassium (Kv) channel, critical region Kv voltage sensor, forms vestibule. S3–S4 interactions are detected at early stage biogenesis. Moreover, vestibule consistent with closed-state conformation channel plasma membrane.