Nanomechanics of HaloTag Tethers

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• 作者：Ionel Popa ; Ronen Berkovich ; Jorge Alegre-Cebollada ; Carmen L. Badilla ; Jaime Andr茅s Rivas-Pardo ; Yukinori Taniguchi ; Masaru Kawakami ; Julio M. Fernandez
• 刊名：Journal of the American Chemical Society
• 出版年：2013
• 出版时间：August 28, 2013
• 年：2013
• 卷：135
• 期：34
• 页码：12762-12771
• 全文大小：615K
• 年卷期：v.135,no.34(August 28, 2013)
• ISSN：1520-5126

文摘

The active site of the Haloalkane Dehydrogenase (HaloTag) enzyme can be covalently attached to a chloroalkane ligand providing a mechanically strong tether, resistant to large pulling forces. Here we demonstrate the covalent tethering of protein L and I27 polyproteins between an atomic force microscopy (AFM) cantilever and a glass surface using HaloTag anchoring at one end and thiol chemistry at the other end. Covalent tethering is unambiguously confirmed by the observation of full length polyprotein unfolding, combined with high detachment forces that range up to 2000 pN. We use these covalently anchored polyproteins to study the remarkable mechanical properties of HaloTag proteins. We show that the force that triggers unfolding of the HaloTag protein exhibits a 4-fold increase, from 131 to 491 pN, when the direction of the applied force is changed from the C-terminus to the N-terminus. Force-clamp experiments reveal that unfolding of the HaloTag protein is twice as sensitive to pulling force compared to protein L and refolds at a slower rate. We show how these properties allow for the long-term observation of protein folding鈥搖nfolding cycles at high forces, without interference from the HaloTag tether.