Hyun-Kyu Choi1,2,3, Duyoung Min4,5, Hyunook Kang2, Min Ju Shon2,3, Sang-Hyun Rah1,2,3, Hak Chan Kim2, Hawoong Jeong1, Hee-Jung Choi6, James U Bowie7, Tae-Young Yoon6,3. 1. Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, South Korea. 2. School of Biological Sciences, Seoul National University, Seoul 08826, South Korea. 3. Institute for Molecular Biology and Genetics, Seoul National University, Seoul 08826, South Korea. 4. Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095, USA. 5. Department of Chemistry, Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea. 6. School of Biological Sciences, Seoul National University, Seoul 08826, South Korea. choihj@snu.ac.kr bowie@mbi.ucla.edu tyyoon@snu.ac.kr. 7. Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095, USA. choihj@snu.ac.kr bowie@mbi.ucla.edu tyyoon@snu.ac.kr.
Abstract
To understand membrane protein biogenesis, we need to explore folding within a bilayer context. Here, we describe a single-molecule force microscopy technique that monitors the folding of helical membrane proteins in vesicle and bicelle environments. After completely unfolding the protein at high force, we lower the force to initiate folding while transmembrane helices are aligned in a zigzag manner within the bilayer, thereby imposing minimal constraints on folding. We used the approach to characterize the folding pathways of the Escherichia coli rhomboid protease GlpG and the human β2-adrenergic receptor. Despite their evolutionary distance, both proteins fold in a strict N-to-C-terminal fashion, accruing structures in units of helical hairpins. These common features suggest that integral helical membrane proteins have evolved to maximize their fitness with cotranslational folding.
To understand membrane protein biogenesis, we need to explore folding within a bilayer context. Here, we describe a single-molecule force microscopy technique that monitors the folding of helical membrane proteins in vesicle and bicelle environments. After completely unfolding the protein at high force, we lower the force to initiate folding while transmembrane helices are aligned in a zigzag manner within the bilayer, thereby imposing minimal constraints on folding. We used the approach to characterize the folding pathways of the n class="Species">Escherichia coli rhomboid protease GlpG and the human β2-adrenergic receptor. Despite their evolutionary distance, both proteins fold in a strict N-to-C-terminal fashion, accruing structures in units of helical hairpins. These common features suggest that integral helical membrane proteins have evolved to maximize their fitness with cotranslational folding.
Authors: Søren G F Rasmussen; Hee-Jung Choi; Daniel M Rosenbaum; Tong Sun Kobilka; Foon Sun Thian; Patricia C Edwards; Manfred Burghammer; Venkata R P Ratnala; Ruslan Sanishvili; Robert F Fischetti; Gebhard F X Schertler; William I Weis; Brian K Kobilka Journal: Nature Date: 2007-10-21 Impact factor: 49.962