Surface-Induced Changes in the Conformation and Glucan Production of Glucosyltransferase Adsorbed on Saliva-Coated Hydroxyapatite


Glucosyltransferases (Gtfs) from S. mutans play critical roles in the development of virulent oral biofilms associated with dental caries disease. Gtfs adsorbed to the tooth surface produce glucans that promote local microbial colonization and provide an insoluble exopolysaccharides (EPS) matrix that facilitates biofilm initiation. Moreover, agents that inhibit the enzymatic activity of Gtfs in solution often have reduced or no effects on surface-adsorbed Gtfs. This study elucidated the mechanisms responsible for the differences in functionality that GtfB exhibits in solution vs surface-adsorbed. Upon adsorption to planar fused-quartz substrates, GtfB displayed a 37% loss of helices and 36% increase of β-sheets, as determined by circular dichroism (CD) spectroscopy, and surface-induced conformational changes were more severe on substrates modified with CH3- and NH2-terminated self-assembled monolayers. GtfB also underwent substantial conformation changes when adsorbing to hydroxyapatite (HA) microspheres, likely due to electrostatic interactions between negatively charged GtfB and positively charged HA crystal faces. Conformational changes were lessened when HA surfaces were coated with saliva (sHA) prior to GtfB adsorption. Furthermore, GtfB remained highly active on sHA, as determined by in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, producing glucans that were structurally different than GtfB in solution and known to increase the accumulation and virulence of biofilms. Our data provide the first insight into the structural underpinnings governing Gtf conformation and enzymatic function that occur on tooth surfaces in vivo, which may lead to designing potent new inhibitors and improved strategies to combat the formation of pathogenic oral biofilms.


Materials Science and Engineering

Keywords and Phrases

Adsorption; Biofilms; Body fluids; Circular dichroism spectroscopy; Dichroism; Enzyme activity; Fourier transform infrared spectroscopy; Hydroxyapatite; Polysaccharides; Quartz, Attenuated total reflectance Fourier transform infrared; Conformation change; Conformational change; Enzymatic activities; Enzymatic functions; Glucosyltransferases; Microbial colonization; Surface-induced conformational changes, Self assembled monolayers, glucan; glucosyltransferase; hydroxyapatite, adsorption; biosynthesis; chemistry; conformation; enzymology; metabolism; particle size; saliva; Streptococcus mutans; surface property, Adsorption; Durapatite; Glucans; Glucosyltransferases; Molecular Conformation; Particle Size; Saliva; Streptococcus mutans; Surface Properties

International Standard Serial Number (ISSN)

0743-7463; 1520-5827

Document Type

Article - Journal

Document Version


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© 2015 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Apr 2015

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