Dataset Information

Structure and Function Characterization of the a1a2 Motifs of Streptococcus pyogenes M Protein in Human Plasminogen Binding.

ABSTRACT: Plasminogen (Plg)-binding M protein (PAM) is a group A streptococcal cell surface receptor that is crucial for bacterial virulence. Previous studies revealed that, by binding to the kringle 2 (KR2) domain of host Plg, the pathogen attains a proteolytic microenvironment on the cell surface that facilitates its dissemination from the primary infection site. Each of the PAM molecules in their dimeric assembly consists of two Plg binding motifs (called the a1 and a2 repeats). To date, the molecular interactions between the a1 repeat and KR2 have been structurally characterized, whereas the role of the a2 repeat is less well defined. Here, we report the 1.7-Å x-ray crystal structure of KR2 in complex with a monomeric PAM peptide that contains both the a1 and a2 motifs. The structure reveals how the PAM peptide forms key interactions simultaneously with two KR2 via the high-affinity lysine isosteres within the a1a2 motifs. Further studies, through combined mutagenesis and functional characterization, show that a2 is a stronger KR2 binder than a1, suggesting that these two motifs may play discrete roles in mediating the final PAM-Plg assembly.

SUBMITTER: Quek AJH

PROVIDER: S-EPMC7722781 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Publications

Structure and Function Characterization of the a1a2 Motifs of Streptococcus pyogenes M Protein in Human Plasminogen Binding.

Quek Adam J H AJH Mazzitelli Blake A BA Wu Guojie G Leung Eleanor W W EWW Caradoc-Davies Tom T TT Lloyd Gordon J GJ Jeevarajah Devadharshini D Conroy Paul J PJ Sanderson-Smith Martina M Yuan Yue Y Ayinuola Yetunde A YA Castellino Francis J FJ Whisstock James C JC Law Ruby H P RHP

Journal of molecular biology 20190708 19

Plasminogen (Plg)-binding M protein (PAM) is a group A streptococcal cell surface receptor that is crucial for bacterial virulence. Previous studies revealed that, by binding to the kringle 2 (KR2) domain of host Plg, the pathogen attains a proteolytic microenvironment on the cell surface that facilitates its dissemination from the primary infection site. Each of the PAM molecules in their dimeric assembly consists of two Plg binding motifs (called the a1 and a2 repeats). To date, the molecular ...[more]

PMID: 31295457

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Project description:Streptococcus pyogenes (Lancefield group A Streptococcus [GAS]) is a ?-hemolytic human-selective pathogen that is responsible for a large number of morbid and mortal infections in humans. For efficient infection, GAS requires different types of surface proteins that provide various mechanisms for evading human innate immune responses, thus enhancing pathogenicity of the bacteria. Many such virulence-promoting proteins, including the major surface signature M protein, are translocated after biosynthesis through the cytoplasmic membrane and temporarily tethered to this membrane via a type 1 transmembrane domain (TMD) positioned near the COOH terminus. In these proteins, a sorting signal, LPXTG, is positioned immediately upstream of the TMD, which is cleaved by the membrane-associated transpeptidase, sortase A (SrtA), leading to the covalent anchoring of these proteins to newly emerging l-Ala-l-Ala cross-bridges of the growing peptidoglycan cell wall. Herein, we show that inactivation of the srtA gene in a skin-tropic pattern D GAS strain (AP53) results in retention of the M protein in the cell membrane. However, while the isogenic AP53 ?srtA strain is attenuated in overall pathogenic properties due to effects on the integrity of the cell membrane, our data show that the M protein nonetheless can extend from the cytoplasmic membrane through the cell wall and then to the surface of the bacteria and thereby retain its important properties of productively binding and activating fluid-phase host plasminogen (hPg). The studies presented herein demonstrate an underappreciated additional mechanism of cell surface display of bacterial virulence proteins via their retention in the cell membrane and extension to the GAS surface.IMPORTANCE Group A Streptococcus pyogenes (GAS) is a human-specific pathogen that produces many surface factors, including its signature M protein, that contribute to its pathogenicity. M proteins undergo specific membrane localization and anchoring to the cell wall via the transpeptidase sortase A. Herein, we explored the role of sortase A function on M protein localization, architecture, and function, employing, a skin-tropic GAS isolate, AP53, which expresses a human plasminogen (hPg)-binding M (PAM) Protein. We showed that PAM anchored in the cell membrane, due to the targeted inactivation of sortase A, was nonetheless exposed on the cell surface and functionally interacted with host hPg. We demonstrate that M proteins, and possibly other sortase A-processed proteins that are retained in the cell membrane, can still function to initiate pathogenic processes by this underappreciated mechanism.

Dataset Information

Structure and Function Characterization of the a1a2 Motifs of Streptococcus pyogenes M Protein in Human Plasminogen Binding.

Publications

Structure and Function Characterization of the a1a2 Motifs of Streptococcus pyogenes M Protein in Human Plasminogen Binding.

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