Forces and Dynamics of Glucose and Inhibitor Binding to Sodium Glucose Co-transporter SGLT1 Studied by Single Molecule Force Spectroscopy

Abstract

Background: SGLT1 functions in intestinal glucose absorption and renal reabsorption. Results: With increasing temperature, width of energy barrier and average life time increased for glucose binding to SGLT1 but decreased for phlorizin binding. Conclusion: Sugar translocation and inhibitor binding involves several steps with different temperature sensitivity. Significance: Force spectroscopy can be used to study dynamics and structure of membrane transporter.

Identification of phlorizin binding domains in sodium-glucose cotransporter family: SGLT1 as a unique model system

“…Such interaction leads to a condensed state of loop 13 followed by major conformational changes [10], similar to what has been observed in the intact human SGLT1 carrier [22]. Evidence for specific conformational arrangements of the aglucone binding site was also obtained in AFM studies on intact cells [23].…”

Characterizing the effect of polymyxin B antibiotics to lipopolysaccharide on Escherichia coli surface using atomic force microscopy

“…Unbinding events within the first peak were used to create an unbinding force vs force loading rate plot for each peak in the force PDF, to show dynamic aspects of the bonds. A maximum likelihood approach was used to fit the width of the energy barrier ( X β ) and the kinetic off‐rate constant ( K off ) for the obtained data by using Evans theory . The Bayesian information criterion was designed to select the best fitting …”

“…21,22 The Bayesian information criterion was designed to select the best fitting. 24,25 Single unbinding events were measured with average unbinding force values of about 30 pN at a retraction velocity of 500 nm/s. Occasionally, unspecific interactions were observed during retraction in a short distance to the contact point, which is ascribed to electrostatic interactions.…”

Characterization of the specific interaction between the DNA aptamer sgc8c and protein tyrosine kinase-7 receptors at the surface of T-cells by biosensing AFM

“…For calculation of k off and x β from the loading rate dependence, all individual rupture events were plotted as a data cloud to account for the influence of the effective spring constant that varies strongly at a given pulling velocity as a result of the position-dependent elasticity of the cell [58]. A fit of the data by a maximum likelihood approach (as described in more detail in [51]) yielded a dissociation constant k off of 5.16 ± 0.19 s −1 with a width of the energy barrier x β of 0.65 ± 0.01 Å. The kinetic off rate is indicative of a slow dissociation of the complex, which is favorable in terms of an extended interacting time between the aptamer and the PTK7 in the cell membrane.…”

“…Each individual rupture force of a single unbinding event was plotted against its individual corresponding force loading rate r (determined from the effective spring constant multiplied by the pulling velocity) and finally merged into a dynamic force spectra plot. The loading rate-dependent unbinding forces were evaluated with a maximum likelihood approach [51] to fit a statistical model based on the Evans theory [52] that allows calculation of the dissociation rate constant (k off ) and the width of the energy barrier x β based on the equation f u (r) = (k B T/x)ln[rx/(k B Tk off )], where x is the separation of the energetic barrier to the equilibrium position, k off the dissociation constant at zero force, k B T the thermal energy, and f u (r) the most probable unbinding force at the loading rate r.…”