Glucan-binding Proteins of the Oral Streptococci

Abstract

ABSTRACT:The synthesis of extracellular glucan is an integral component of the sucrose-dependent colonization of tooth surfaces by species of the mutans streptococci. In investigators' attempts to understand the mechanisms of plaque biofilm development, several glucan-binding proteins (GBPs) have been discovered. Some of these, the glucosyltransferases, catalyze the synthesis of glucan, whereas others, designated only as glucan-binding proteins, have affinities for different forms of glucan and contribute to aspects of the biology of their host organisms. The functions of these latter glucan-binding proteins include dextran-dependent aggregation, dextranase inhibition, plaque cohesion, and perhaps cell wall synthesis. In some instances, their glucan-binding domains share common features, whereas in others the mechanism for glucan binding remains unknown. Recent studies indicate that at least some of the glucan-binding proteins modulate virulence and some can act as protective immunogens within animal models. Overall, the multiplicity of GBPs and their aforementioned properties are testimonies to their importance. Future studies will greatly advance the understanding of the distribution, function, and regulation of the GBPs and place into perspective the facets of their contributions to the biology of the oral streptococci.

Streptococcus mutans: a new Gram-positive paradigm?

“…During this period, the first tools for studying S. mutans, both in vitro and in vivo, were developed. As a result of the efforts of these pioneer researchers, the major virulence traits of S. mutans were established: (i) the ability to produce large quantities of organic acids (acidogenicity) from metabolized carbohydrates; (ii) the ability to survive at low pH (aciduricity); and (iii) the ability to synthesize extracellular glucan-homopolymers from sucrose, which play a critical role in initial attachment, colonization and accumulation of biofilms on tooth surfaces (Banas & Vickerman, 2003;Bowen & Koo, 2011;Burne, 1998;Loesche, 1986). With the advances in molecular genetic techniques in the 1980s and 90s, scientists began to more rapidly understand how metabolic pathways enabled S. mutans to evolve into a specialized dental pathogen.…”

“…mutans-derived extracellular glucosyltransferases (Gtfs) are constituents of the pellicle and are capable of synthesizing glucans in situ from sucrose (Schilling & Bowen, 1992). The surface-formed glucans provide additional bacterial binding sites that favour local colonization by S. mutans, as it binds avidly and in large numbers to these polymers (Schilling & Bowen, 1992) through several envelope-associated glucanbinding proteins (Banas & Vickerman, 2003). Furthermore, in situ-formed glucans can mask host-derived bacterial binding sites in the pellicle (Schilling & Bowen, 1992), which may negatively impact adherence of other commensal species that bind more favourably to the pellicle, such as Streptococcus oralis, S. sanguinis and S. gordonii (Jenkinson, 2011;Nobbs et al, 2009).…”

“…While a normal inhabitant of the oral cavity, S. mutans is mostly known for its importance in the aetiology of dental caries and occasional association with subacute infective endocarditis. Decades of research have conclusively demonstrated that S. mutans is a major cariogenic organism by virtue of its contribution to the formation of the dental biofilm matrix, its capacity to produce large quantities of organic acids, and its ability to outcompete non-cariogenic commensal species at low pH conditions (Banas & Vickerman, 2003;Bowen & Koo, 2011;Gross et al, 2012;Lemos et al, 2005;Quivey et al, 2001).…”

Longitudinal comparison of Streptococcus mutans-induced aggravation of non-alcoholic steatohepatitis in mice

“…Moreover, the cell-surface protein antigens of S. mutans , including glucosyltransferases, 190-k Da protein antigens (PA), and glucan-binding proteins, are known to be associated with the severity of dental caries [2–4]. In addition, Cnm, a collagen-binding protein, has been purified and its encoding gene, cnm , sequenced [5].…”

The ability of IgY to recognize surface proteins of Streptococcus mutans

“…3 Molecularly, the surface proteins of S. mutans that are commonly involved in the process of dental caries are Glucan binding protein (Gbp) and Antigen I/II (Ag I/II). 4,5 Besides that, S. mutans also express molecules as enzyme in the process of carbohydrate fermentation that has a role in the activity of S. mutans, such as Glucosyltransferase (Gtf), Dextranase (Dex), and Fruktosiltranferase (Ftf). Each of those three enzymes then breaks sucrose in order to form glukan, dextran, and fruktan.…”