title: Surface-induced changes in the conformation and glucan production of glucosyltransferase adsorbed on saliva-coated hydroxyapatite.
abstract: 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.
authors: †Chemistry Division, U.S. Naval Research Laboratory, Washington, D.C. 20375, United States.
authors: Kenan P
authors: KP
authors: Fears
authors: ‡Department of Dentistry and Center for Oral Biology, University of Rochester Medical Center, Rochester, New York 14642, United States.
authors: Mireya
authors: M
authors: Gonzalez-Begne
authors: †Chemistry Division, U.S. Naval Research Laboratory, Washington, D.C. 20375, United States.
authors: Corey T
authors: CT
authors: Love
authors: §Department of Materials Science and Engineering and Center for Bone and Tissue Repair and Regeneration, Missouri University of Science and Technology, Rolla, Missouri 65409, United States.
authors: Delbert E
authors: DE
authors: Day
authors: ∥Biofilm Research Laboratories, Levy Center for Oral Health, Department of Orthodontics and Division of Pediatric Dentistry and Community Oral Health, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
authors: Hyun
authors: H
authors: Koo
mesh_terms: D000327:Adsorption; D017886:Durapatite / Q000737:chemistry* / Q000378:metabolism; D005936:Glucans / Q000096:biosynthesis* / Q000737:chemistry; D005964:Glucosyltransferases / Q000737:chemistry* / Q000378:metabolism*; D008968:Molecular Conformation; D010316:Particle Size; D012463:Saliva / Q000737:chemistry* / Q000378:metabolism; D013295:Streptococcus mutans / Q000201:enzymology / Q000378:metabolism; D013499:Surface Properties
chemical_list: D005936:Glucans; D017886:Durapatite; D005964:Glucosyltransferases