<em><em>In Silico</em></em> Analysis of Possible Surface associated Proteins of the Oral Pathogen <em><em>S. mutans</em></em>

Research Article

J Dent & Oral Disord. 2016; 2(2): 1011.

In Silico Analysis of Possible Surface associated Proteins of the Oral Pathogen S. mutans

Schuessler DL, Brenner LM, Wolff D and Wolff B*

Department of Conservative Dentistry, School of Dental Medicine, Ruprecht Karls University, Heidelberg, Germany

*Corresponding author: Wolff B, Department of Conservative Dentistry, University of Heidelberg, School of Dental Medicine, Heidelberg, Germany

Received: March 07, 2016; Accepted: April 06, 2016; Published: April 08, 2016

Abstract

Streptococcus mutans is a gram-positive pathogen associated with dental caries in humans, thereby posing a significant strain on public health. Bacterial surface associated proteins are important for virulence and pathogenesis. Since these proteins are likely to be targets of the host’s immune defense, they could also be important for vaccine development.

In this study three different protein prediction algorithms (PSORTb, CELLO and LocTree) were used to identify possible cell-surface associated proteins of S. mutans UA159. This In Silico approach allowed the prediction of 48 potential surface-associated proteins. The data reported here might help to identify possible candidates for development of diagnostic agents, drugs and vaccines against S. mutans.

Keywords: Subcellular protein localization (SCL) programs; Surface associated proteins; Streptococcus mutans; Biofilm formation

Introduction

Whilst oral biofilms, which can consist of up to 700 different species, are closely linked to oral disease, several specific pathogens and their surface proteins have been associated with playing major roles in oral biofilm formation and disease development [1]. Interactions between these species play significant roles in pathogenesis [2]. There is particular interest in the key pathogen involved in caries, Streptococcus mutans, which is thought to be a major global health burden [3-5]. S. mutans is known to play a leading part in the development of cariogenic lesions, and is frequently found in biofilms extracted from carious dentin [6-8].

Bacterial surface-associated proteins are important for virulence and pathogenesis [9]. Several known virulence factors of S. mutans are extracellular, may it be cell-surface associated or secreted. For example, S. mutans is able to build extracellular glucanpolymers from saccharose using glucosyltransferases, allowing it to adhere to tooth enamel, and establish biofilm formation [10]. Some strains of S. mutans produce proteases which can de-activate IgA-antibodies in saliva and thus weaken the host’s immune defense [11]. Since surface proteins are likely to be targets of the host’s immune defense, they could also be important for vaccine development [12].

The aim of this study was to identify possible cell-surface associated proteins of S. mutans UA159 which could be potential new diagnostic, drug and vaccine targets. An In Silico approach using three different protein prediction algorithms (PSORTb, CELLO and LocTree) was applied to search for candidate proteins. A literature research was conducted to verify the predicted subcellular localization or function of these proteins where possible.

Materials and Methods

In Silico analysis

In this analysis Subcellular Protein Localization (SCL) programs were employed to identify potential cell-surface associated proteins of S. mutans UA159 [13]. Three programs, with high prediction coverage (>75%) and accuracy in Gram-positive bacteria, were specifically selected: PSORTb Version 3.0, Cello v.2.5. and LocTree3 [14-18]. The whole genomic sequence of S. mutans UA159 [13] was analyzed in the PSORTdb using the PSORTb Version 3.0 algorithm [14,19]. From the PSORTb prediction results proteins within the predicted localization categories “cell wall”, “extracellular” and “unknown/ multiple localization” were short-listed as being possibly surface associated. FASTA sequences of these short-listed proteins were then run through the CELLO v.2.5 and the LocTree3 programs [15-18].

A review of the literature available to date on the short-listed proteins was carried out using the PubMed NCBI database (www. ncbi.nlm.nih.gov/pubmed). Keywords used were the locus tag and/ or the definition of the shortlisted proteins, as well as the terms “Streptococcus mutans”. In case the search yielded no published data on the protein in S. mutans, search terms “streptococcus”, or “bacterial” were used. Where applicable, studies relating to the protein’s function, experimentally verifying or implying an extracellular, cell wall or surface associated localization in either S. mutans, streptococci or other bacterial species were included. In the case of no or sparse available literature pertaining to function or localization (for example hypothetical proteins), studies showing their up- or down regulation under certain conditions were included where possible.

Results

Assuming that cell-surface associated proteins could be found in several localizations proteins included in the following predicted categories of localization by PSORTb were short-listed: extracellular, cell wall, and multiple localizations. The resulting 48 candidates for potential cell-surface associated proteins, their predicted subcellular localization by CELLO and LocTree, and the literature available on their putative localization are listed in Table 1.

PSORTb predicted 24 proteins with an extracellular localization. These include the glucosyltransferases GtfB, GtfD and GtfC; the glucanbinding protein GbpA; the secreted antigen GbpB/SagA;the glucanbinding protein GbpD; the competence stimulating peptide (CSP) ComC; the bacteriocin peptideBsmE;the autolysin LytF; an autolysin/ amidase (SMU_704c); the manganese-type superoxide dismutase SodA; a permease (SMU_862); the β-D-fructosyltransferaseSacB; thex-prolyl-dipeptidylaminopeptidasePepX;a peptidoglycandeacetylase PgdB; two transposase fragments (SMU_1024c and SMU_1358); the cytoplasmic a-amylase Amy; and 4 hypothetical proteins (SMU_616, SMU_1752c, SMU_1882c, and SMU_2048). The predicted extracellular or secreted localization concurred with the CELLO and LocTree results for all but 3 proteins (Table 1). CELLO predicted PepX to be cytoplasmic, PgdBto be located in the membrane, and Amy to be cytoplasmic. In contrast to this, LocTree assigned all 3 a secreted localization, in agreement with the PSORTb result (Table 1).

Citation:Schuessler DL, Brenner LM, Wolff D and Wolff B. In Silico Analysis of Possible Surface associated Proteins of the Oral Pathogen S. mutans. J Dent & Oral Disord. 2016; 2(2): 1011. ISSN:2572-7710