N. Bavi, O. Bavi, M. Vossoughi, R. Naghdabadi, A. Hill, B. Martinac, Y. Jamali
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Nanomechanical properties of MscL α helices: A steered molecular dynamics study
ABSTRACT Gating of mechanosensitive (MS) channels is driven by a hierarchical cascade of movements and deformations of transmembrane helices in response to bilayer tension. Determining the intrinsic mechanical properties of the individual transmembrane helices is therefore central to understanding the intricacies of the gating mechanism of MS channels. We used a constant-force steered molecular dynamics (SMD) approach to perform unidirectional pulling tests on all the helices of MscL in M. tuberculosis and E. coli homologs. Using this method, we could overcome the issues encountered with the commonly used constant-velocity SMD simulations, such as low mechanical stability of the helix during stretching and high dependency of the elastic properties on the pulling rate. We estimated Young's moduli of the α-helices of MscL to vary between 0.2 and 12.5 GPa with TM2 helix being the stiffest. We also studied the effect of water on the properties of the pore-lining TM1 helix. In the absence of water, this helix exhibited a much stiffer response. By monitoring the number of hydrogen bonds, it appears that water acts like a ‘lubricant’ (softener) during TM1 helix elongation. These data shed light on another physical aspect underlying hydrophobic gating of MS channels, in particular MscL.
期刊介绍:
Channels is an open access journal for all aspects of ion channel research. The journal publishes high quality papers that shed new light on ion channel and ion transporter/exchanger function, structure, biophysics, pharmacology, and regulation in health and disease.
Channels welcomes interdisciplinary approaches that address ion channel physiology in areas such as neuroscience, cardiovascular sciences, cancer research, endocrinology, and gastroenterology. Our aim is to foster communication among the ion channel and transporter communities and facilitate the advancement of the field.