Atomic Force Microscopy of Biological Membranes

Frederix, P. L. T. M.; Bosshart, Patrick D.; Engel, Andréas

doi:10.1016/j.bpj.2008.09.046

Cited by 115 publications

(75 citation statements)

References 80 publications

(89 reference statements)

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“…53,54 AFM imaging herein of cleaned evaporated gold surfaces (rms roughness 1.1 nm) exposed to dilute solutions of wild-type BR showed clear evidence of patches which ranged from a few tens to hundreds of square nanometers (Figure 2) with typical coverage ranging from 8% to 40% (20 μM solution incubations varying from 1 hour to overnight) of the available surface. Upon removal of the lipid from the purple membrane (wild-type and mutant), the individual trimers were released.…”

Section: ' Results and Discussionmentioning

confidence: 99%

Enhanced Photocurrent in Engineered Bacteriorhodopsin Monolayer

et al. 2011

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Section: ' Results and Discussionmentioning

confidence: 99%

Enhanced Photocurrent in Engineered Bacteriorhodopsin Monolayer

et al. 2011

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“…The singleparticle reconstruction shows the ligand-binding domains disposed in a fourfold symmetric arrangement. Despite this structural information, there is still a lack of understanding about the conformational changes that occur in the MlotiK1 channel upon ligand-binding.Atomic force microscopy (AFM) has been established to observe the surfaces of membrane proteins at high resolution (0.5-2 nm) in their native state (13,14). Importantly for biological applications, AFM requires no labeling or staining and allows imaging of membrane proteins in the lipid membrane, in buffer solution, and at ambient temperature (15,16).…”

mentioning

confidence: 99%

“…Atomic force microscopy (AFM) has been established to observe the surfaces of membrane proteins at high resolution (0.5-2 nm) in their native state (13,14). Importantly for biological applications, AFM requires no labeling or staining and allows imaging of membrane proteins in the lipid membrane, in buffer solution, and at ambient temperature (15,16).…”

mentioning

confidence: 99%

Gating of the MlotiK1 potassium channel involves large rearrangements of the cyclic nucleotide-binding domains

Mari

Pessoa

Altieri

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Cyclic nucleotide-regulated ion channels are present in bacteria, plants, vertebrates, and humans. In higher organisms, they are closely involved in signaling networks of vision and olfaction. Binding of cAMP or cGMP favors the activation of these ion channels. Despite a wealth of structural and studies, there is a lack of structural data describing the gating process in a full-length cyclic nucleotideregulated channel. We used high-resolution atomic force microscopy (AFM) to directly observe the conformational change of the membrane embedded bacterial cyclic nucleotide-regulated channel MlotiK1. In the nucleotide-bound conformation, the cytoplasmic cyclic nucleotide-binding (CNB) domains of MlotiK1 are disposed in a fourfold symmetric arrangement forming a pore-like vestibule. Upon nucleotide-unbinding, the four CNB domains undergo a large rearrangement, stand up by ∼1.7 nm, and adopt a structurally variable grouped conformation that closes the cytoplasmic vestibule. This fully reversible conformational change provides insight into how CNB domains rearrange when regulating the potassium channel.conformational changes | cyclic nucleotide gating | membrane protein | MloK1 | single-molecule imaging P otassium channels are tetrameric membrane proteins that facilitate the permeation of potassium ions through the membrane with high specificity and high-throughput rates. These channels are central to the electrical activity of cells in humans and are, therefore, of fundamental importance for the function of nervous and muscular systems. The major mode of functional regulation in potassium channels is gating, a conformational change that occurs on the intracellular regions of the ion pore domain and involves an iris-like movement of the C-terminal transmembrane helices and a widening of the intracellular pore. Gating in potassium channels is induced by a variety of stimuli, including membrane voltage, intracellular calcium concentration, and cyclic nucleotide levels (1). These stimuli are sensed by a separate domain from the ion pore domain, inducing a conformational change that is then propagated to the gate of the channel.The MlotiK1 potassium channel, from the bacterium Mesorhizobium loti, belongs to the family of channels that is regulated by cyclic nucleotides and includes eukaryotic cyclic nucleotide-gated (CNG) and hyperpolarization activated cyclic nucleotide-gated (HCN) channels (2, 3). These channels have C-terminal cytoplasmic cyclic nucleotide-binding (CNB) domains and upon binding of cAMP or cGMP, these domains undergo a conformational change that favors the opening of the gate of the channel. The major difference between the MlotiK1 channel and the CNG or HCN channels is the linker that connects the gate to the CNB domains. This helical linker (C linker) is roughly 80 residues long in CNG and HCN channels and only ∼20 residues long in the MlotiK1 channel.The MlotiK1 channel has been the focus of structural and functional studies with the aim of understanding channel regulation by cyclic nucleotides. X-ray...

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“…They are prepared using various techniques like vesicle deposition, Langmuir-Blodgett method and spin-coating 8,9 . AFM imaging has been used to follow the formation of these supported bilayers 10 , and probe different structures formed by membranes of different compositions [11][12][13][14][15] .…”

Section: Introductionmentioning

confidence: 99%

Atomic Force Microscopy Imaging and Force Spectroscopy of Supported Lipid Bilayers

Unsay

Cosentino

García‐Sáez

2015

JoVE

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Atomic force microscopy (AFM) is a versatile, high-resolution imaging technique that allows visualization of biological membranes. It has sufficient magnification to examine membrane substructures and even individual molecules. AFM can act as a force probe to measure interactions and mechanical properties of membranes. Supported lipid bilayers are conventionally used as membrane models in AFM studies. In this protocol, we demonstrate how to prepare supported bilayers and characterize their structure and mechanical properties using AFM. These include bilayer thickness and breakthrough force.The information provided by AFM imaging and force spectroscopy help define mechanical and chemical properties of membranes. These properties play an important role in cellular processes such as maintaining cell hemostasis from environmental stress, bringing membrane proteins together, and stabilizing protein complexes. Video LinkThe video component of this article can be found at

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Atomic Force Microscopy of Biological Membranes

Cited by 115 publications

References 80 publications

Enhanced Photocurrent in Engineered Bacteriorhodopsin Monolayer

Enhanced Photocurrent in Engineered Bacteriorhodopsin Monolayer

Gating of the MlotiK1 potassium channel involves large rearrangements of the cyclic nucleotide-binding domains

Atomic Force Microscopy Imaging and Force Spectroscopy of Supported Lipid Bilayers

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