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Structure of the C-terminal domain of AspA (antigen I/II-family) protein from Streptococcus pyogenes.

Hall M, Nylander S, Jenkinson HF, Persson K - FEBS Open Bio (2014)

Bottom Line: The antigen I/II family proteins are cell wall anchored adhesin proteins found on the surfaces of most oral streptococci and are involved in host colonization and biofilm formation.Despite relatively low sequence identity, interestingly, the overall structure shares high similarity to the C2-3-domains of antigen I/II proteins from Streptococcus gordonii and Streptococcus mutans, although certain parts of the structure exhibit distinct features.In summary this work constitutes the first step in the full structure determination of the AspA protein from S. pyogenes.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.

ABSTRACT
The pathogenic bacteria Streptococcus pyogenes can cause an array of diseases in humans, including moderate infections such as pharyngitis (strep throat) as well as life threatening conditions such as necrotizing fasciitis and puerperal fever. The antigen I/II family proteins are cell wall anchored adhesin proteins found on the surfaces of most oral streptococci and are involved in host colonization and biofilm formation. In the present study we have determined the crystal structure of the C2-3-domain of the antigen I/II type protein AspA from S. pyogenes M type 28. The structure was solved to 1.8 Å resolution and shows that the C2-3-domain is comprised of two structurally similar DEv-IgG motifs, designated C2 and C3, both containing a stabilizing covalent isopeptide bond. Furthermore a metal binding site is identified, containing a bound calcium ion. Despite relatively low sequence identity, interestingly, the overall structure shares high similarity to the C2-3-domains of antigen I/II proteins from Streptococcus gordonii and Streptococcus mutans, although certain parts of the structure exhibit distinct features. In summary this work constitutes the first step in the full structure determination of the AspA protein from S. pyogenes.

No MeSH data available.


Related in: MedlinePlus

Comparative structural and evolutionary conservation analyses of AspA-C2–3. (A) Superposition of the AspA-C2–3 structure (blue) with the structures of SspB-C2-3 from S. gordonii (orange, PDB: 2WOY) and SpaP-C2–3 from S. mutans (green, PDB: 3OPU). The BAR (SspB Adherence Region), recognized by P. gingivalis short fimbrial protein Mfa1, is highlighted by a black circle and is shown in more detail as a stereo image in (B) together with a sequence alignment of the BAR helix. (C) Space filling model representation of evolutionary conservation analyses for AspA-C2–3 performed using ConSurf [25]. The level of conservation of individual amino acids is indicated from variable (turquoise, 1) to highly conserved (maroon, 9) according to the color coding bar. Positions for which the level of conservation was assigned with low confidence are marked with yellow color. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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f0020: Comparative structural and evolutionary conservation analyses of AspA-C2–3. (A) Superposition of the AspA-C2–3 structure (blue) with the structures of SspB-C2-3 from S. gordonii (orange, PDB: 2WOY) and SpaP-C2–3 from S. mutans (green, PDB: 3OPU). The BAR (SspB Adherence Region), recognized by P. gingivalis short fimbrial protein Mfa1, is highlighted by a black circle and is shown in more detail as a stereo image in (B) together with a sequence alignment of the BAR helix. (C) Space filling model representation of evolutionary conservation analyses for AspA-C2–3 performed using ConSurf [25]. The level of conservation of individual amino acids is indicated from variable (turquoise, 1) to highly conserved (maroon, 9) according to the color coding bar. Positions for which the level of conservation was assigned with low confidence are marked with yellow color. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Mentions: While S. mutans SpaP-C2–3 and S. gordonii SspB-C2–3 share 64% sequence identity (for 332 aligned amino acids), Asp-C2–3 only shares 36% (326 aligned amino acids) and 34% (317 aligned amino acids) sequence identity with SpaP-C2–3 and SspB-C2–3, respectively. Despite the low overall sequence identity the structure of AspA-C2–3 is very similar to that of S. mutans SpaP-C2–3 (r.m.s.d. 1.84 Å) and S. gordonii SspB-C2–3 (r.m.s.d 1.9 Å) (Fig. 4A). The main region of difference is found in and in proximity to the α-helix (DH1) lying perpendicular to the C2-domain central DEv-IgG motif. In S. gordonii SspB this region has been described as a recognition handle for the short fimbria Mfa1 from the periodontal pathogen Porphyromonas gingivalis and is referred to as BAR (for SspB Adherence Region) [23]. Within BAR, two structural motifs, corresponding to the DH1-helix and the loop region following it, have been identified as being important for P. gingivalis binding [5,24]. Interestingly, although the structures of SpaP-C2–3 and SspB-C2–3 are highly similar, also in secondary structure in BAR [7], P. gingivalis does not bind to S. mutans SpaP [23]. It rather appears that the binding is dependent on the specific composition of BAR, perhaps especially on the surface charge distribution around the α-helix. The AspA-C2–3 BAR helix also has a variable amino acid sequence, (DDKLKALIKAS, as compared to KKVQDLLKK in SspB and QEIRDVLSK in SpaP) which gives BAR a different surface charge distribution pattern compared to both SspB and SpaP (Fig. 4B). Also in the AspA-C2–3 structure, residues D1066 and T1067 produce a distinct bulge in the short loop preceding the BAR helix, which protrudes from the protein surface. The interactions in which BAR of AspA may play a role and how these structural features may be involved remains unknown and requires further study. Of additional note is that all three AgI/II type proteins for which the structure of the C2–3 domain has been determined so far (AspA, SspB, SpaP) have bound Ca2+ ions located after the short loop following the DH1 α-helix, which are thought to stabilize the position of the helix. In order to better understand the differences and variability among the C-terminal domains of the AgI/II type proteins, the AspA-C2–3 structure was subjected to evolutionary conservation analysis using ConSurf [16,25]. For the ConSurf analysis 51 homologous sequences were collected using a BLAST search and subsequently used for multiple sequence alignment and evolutionary conservation analysis. The level of conservation of each amino acid, on a scale from 1–9 (where 1 = variable and 9 = very highly conserved), was mapped onto the structural model (Fig. 4C). In good agreement with the observations discussed above, the conservation analysis shows that BAR, and the BAR helix in particular, is highly variable, while the closely located Ca2+ binding pocket in contrast is well conserved. Generally the β-sheet residues with side chains pointing to the interior of the central DEv-IgG motifs in each domain, constituting the hydrophobic core, are well conserved, while those with surface exposed side chains are variable. This is especially evident for one side of the C3 domain (Fig. 4C, right).


Structure of the C-terminal domain of AspA (antigen I/II-family) protein from Streptococcus pyogenes.

Hall M, Nylander S, Jenkinson HF, Persson K - FEBS Open Bio (2014)

Comparative structural and evolutionary conservation analyses of AspA-C2–3. (A) Superposition of the AspA-C2–3 structure (blue) with the structures of SspB-C2-3 from S. gordonii (orange, PDB: 2WOY) and SpaP-C2–3 from S. mutans (green, PDB: 3OPU). The BAR (SspB Adherence Region), recognized by P. gingivalis short fimbrial protein Mfa1, is highlighted by a black circle and is shown in more detail as a stereo image in (B) together with a sequence alignment of the BAR helix. (C) Space filling model representation of evolutionary conservation analyses for AspA-C2–3 performed using ConSurf [25]. The level of conservation of individual amino acids is indicated from variable (turquoise, 1) to highly conserved (maroon, 9) according to the color coding bar. Positions for which the level of conservation was assigned with low confidence are marked with yellow color. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4048849&req=5

f0020: Comparative structural and evolutionary conservation analyses of AspA-C2–3. (A) Superposition of the AspA-C2–3 structure (blue) with the structures of SspB-C2-3 from S. gordonii (orange, PDB: 2WOY) and SpaP-C2–3 from S. mutans (green, PDB: 3OPU). The BAR (SspB Adherence Region), recognized by P. gingivalis short fimbrial protein Mfa1, is highlighted by a black circle and is shown in more detail as a stereo image in (B) together with a sequence alignment of the BAR helix. (C) Space filling model representation of evolutionary conservation analyses for AspA-C2–3 performed using ConSurf [25]. The level of conservation of individual amino acids is indicated from variable (turquoise, 1) to highly conserved (maroon, 9) according to the color coding bar. Positions for which the level of conservation was assigned with low confidence are marked with yellow color. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Mentions: While S. mutans SpaP-C2–3 and S. gordonii SspB-C2–3 share 64% sequence identity (for 332 aligned amino acids), Asp-C2–3 only shares 36% (326 aligned amino acids) and 34% (317 aligned amino acids) sequence identity with SpaP-C2–3 and SspB-C2–3, respectively. Despite the low overall sequence identity the structure of AspA-C2–3 is very similar to that of S. mutans SpaP-C2–3 (r.m.s.d. 1.84 Å) and S. gordonii SspB-C2–3 (r.m.s.d 1.9 Å) (Fig. 4A). The main region of difference is found in and in proximity to the α-helix (DH1) lying perpendicular to the C2-domain central DEv-IgG motif. In S. gordonii SspB this region has been described as a recognition handle for the short fimbria Mfa1 from the periodontal pathogen Porphyromonas gingivalis and is referred to as BAR (for SspB Adherence Region) [23]. Within BAR, two structural motifs, corresponding to the DH1-helix and the loop region following it, have been identified as being important for P. gingivalis binding [5,24]. Interestingly, although the structures of SpaP-C2–3 and SspB-C2–3 are highly similar, also in secondary structure in BAR [7], P. gingivalis does not bind to S. mutans SpaP [23]. It rather appears that the binding is dependent on the specific composition of BAR, perhaps especially on the surface charge distribution around the α-helix. The AspA-C2–3 BAR helix also has a variable amino acid sequence, (DDKLKALIKAS, as compared to KKVQDLLKK in SspB and QEIRDVLSK in SpaP) which gives BAR a different surface charge distribution pattern compared to both SspB and SpaP (Fig. 4B). Also in the AspA-C2–3 structure, residues D1066 and T1067 produce a distinct bulge in the short loop preceding the BAR helix, which protrudes from the protein surface. The interactions in which BAR of AspA may play a role and how these structural features may be involved remains unknown and requires further study. Of additional note is that all three AgI/II type proteins for which the structure of the C2–3 domain has been determined so far (AspA, SspB, SpaP) have bound Ca2+ ions located after the short loop following the DH1 α-helix, which are thought to stabilize the position of the helix. In order to better understand the differences and variability among the C-terminal domains of the AgI/II type proteins, the AspA-C2–3 structure was subjected to evolutionary conservation analysis using ConSurf [16,25]. For the ConSurf analysis 51 homologous sequences were collected using a BLAST search and subsequently used for multiple sequence alignment and evolutionary conservation analysis. The level of conservation of each amino acid, on a scale from 1–9 (where 1 = variable and 9 = very highly conserved), was mapped onto the structural model (Fig. 4C). In good agreement with the observations discussed above, the conservation analysis shows that BAR, and the BAR helix in particular, is highly variable, while the closely located Ca2+ binding pocket in contrast is well conserved. Generally the β-sheet residues with side chains pointing to the interior of the central DEv-IgG motifs in each domain, constituting the hydrophobic core, are well conserved, while those with surface exposed side chains are variable. This is especially evident for one side of the C3 domain (Fig. 4C, right).

Bottom Line: The antigen I/II family proteins are cell wall anchored adhesin proteins found on the surfaces of most oral streptococci and are involved in host colonization and biofilm formation.Despite relatively low sequence identity, interestingly, the overall structure shares high similarity to the C2-3-domains of antigen I/II proteins from Streptococcus gordonii and Streptococcus mutans, although certain parts of the structure exhibit distinct features.In summary this work constitutes the first step in the full structure determination of the AspA protein from S. pyogenes.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.

ABSTRACT
The pathogenic bacteria Streptococcus pyogenes can cause an array of diseases in humans, including moderate infections such as pharyngitis (strep throat) as well as life threatening conditions such as necrotizing fasciitis and puerperal fever. The antigen I/II family proteins are cell wall anchored adhesin proteins found on the surfaces of most oral streptococci and are involved in host colonization and biofilm formation. In the present study we have determined the crystal structure of the C2-3-domain of the antigen I/II type protein AspA from S. pyogenes M type 28. The structure was solved to 1.8 Å resolution and shows that the C2-3-domain is comprised of two structurally similar DEv-IgG motifs, designated C2 and C3, both containing a stabilizing covalent isopeptide bond. Furthermore a metal binding site is identified, containing a bound calcium ion. Despite relatively low sequence identity, interestingly, the overall structure shares high similarity to the C2-3-domains of antigen I/II proteins from Streptococcus gordonii and Streptococcus mutans, although certain parts of the structure exhibit distinct features. In summary this work constitutes the first step in the full structure determination of the AspA protein from S. pyogenes.

No MeSH data available.


Related in: MedlinePlus