Cotranslational membrane insertion of the voltage-sensitive K plus channel KvAP

• 成果类型: Article
• 署名作者: Westerfield, Justin M.; Kozojedova, Petra; Juli, Cara; Metola, Ane; von Heijne, Gunnar
• 署名单位: Stockholm University; Stockholm University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11050
• DOI: 10.1073/pnas.2412492122
• 发表日期: 2025-04-08
• 关键词: high-level expression; translation arrest; nascent polypeptide; sensor domain; protein; RECOGNITION; MOVEMENT; residues; secm

摘要

Voltage-sensor domains (VSDs), found in many voltage-sensitive ion channels and enzymes, are composed of four transmembrane helices (TMHs), including the atypical, highly positively charged S4 helix. VSDs are cotranslationally inserted into the membrane, raising the question of how the highly charged S4 helix is integrated into the lipid bilayer as it exits the ribosome. Here, we have used force profile analysis (FPA) to follow the cotranslational insertion of the six-TMH KvAP voltage-sensitive ion channel into the Escherichia coli inner membrane. We find that the insertion process proceeds through three semi-independent steps: i) insertion of the S1-S2 helix hairpin, ii) insertion of the S3-S5 helices, and iii) insertion of the Pore and S6 helices. Our analysis highlights the importance of the concerted insertion of helical hairpins, the dramatic influence of the positively charged residues in S4, and the unexpectedly strong forces and effects on downstream TMHs elicited by amphipathic and re-entrant helices.