Please use this identifier to cite or link to this item:
|Title:||Structural studies of the mechanism for biosensing antibiotics in a fluorescein-labeled β-lactamase|
Beta lactam antibiotics
|Publisher:||BioMed Central Ltd.|
|Source:||BMC structural biology, 2011, v. 11, 15, p. 1-8 How to cite?|
|Journal:||BMC structural biology|
|Abstract:||Background: β-lactamase conjugated with environment-sensitive fluorescein molecule to residue 166 on the Ω-loop near its catalytic site is a highly effective biosensor for β-lactam antibiotics. Yet the molecular mechanism of such fluorescence-based biosensing is not well understood.|
Results: Here we report the crystal structure of a Class A β-lactamase PenP from Bacillus licheniformis 749/C with fluorescein conjugated at residue 166 after E166C mutation, both in apo form (PenP-E166Cf) and in covalent complex form with cefotaxime (PenP-E166Cf-cefotaxime), to illustrate its biosensing mechanism. In the apo structure the fluorescein molecule partially occupies the antibiotic binding site and is highly dynamic. In the PenPE166Cf-cefatoxime complex structure the binding and subsequent acylation of cefotaxime to PenP displaces fluorescein from its original location to avoid steric clash. Such displacement causes the well-folded Ω-loop to become fully flexible and the conjugated fluorescein molecule to relocate to a more solvent exposed environment, hence enhancing its fluorescence emission. Furthermore, the fully flexible Ω-loop enables the narrow-spectrum PenP enzyme to bind cefotaxime in a mode that resembles the extended-spectrum β-lactamase.
Conclusions: Our structural studies indicate the biosensing mechanism of a fluorescein-labelled β-lactamase. Such findings confirm our previous proposal based on molecular modelling and provide useful information for the rational design of β-lactamase-based biosensor to detect the wide spectrum of β-lactam antibiotics. The observation of increased Ω-loop flexibility upon conjugation of fluorophore may have the potential to serve as a screening tool for novel β-lactamase inhibitors that target the Ω-loop and not the active site.
|Rights:||© 2011 Wong et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.|
|Appears in Collections:||Journal/Magazine Article|
Show full item record
Files in This Item:
|Wong_Structural_studies_mechanism.pdf||700.68 kB||Adobe PDF||View/Open|
Citations as of Jul 21, 2016
WEB OF SCIENCETM
Citations as of Nov 28, 2016
Checked on Nov 27, 2016
Checked on Nov 27, 2016
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.