Structural conservation, variability, and immunogenicity of the T6 backbone pilin of serotype M6 Streptococcus pyogenes.

[acute rheumatic fever]

Group A streptococcus (GAS ; Streptococcus pyogenes ) is a Gram -positive human pathogen that causes a broad range of diseases ranging from acute pharyngitis to the poststreptococcal sequelae of acute rheumatic fever . GAS pili are highly diverse , long protein polymers that extend from the cell surface . They have multiple roles in infection and are promising candidates for vaccine development . This study describes the structure of the T 6 backbone pilin (BP ; Lancefield T -antigen ) from the important M 6 serotype . The structure reveals a modular arrangement of three tandem immunoglobulin-like domains , two with internal isopeptide bonds . The T 6 pilin lysine , essential for polymerization , is located in a novel VAKS motif that is structurally homologous to the canonical YPKN pilin lysine in other three - and four -domain Gram -positive pilins . The T 6 structure also highlights a conserved pilin core whose surface is decorated with highly variable loops and extensions . Comparison to other Gram -positive BPs shows that many of the largest variable extensions are found in conserved locations . Studies with sera from patients diagnosed with GAS -associated acute rheumatic fever showed that each of the three T 6 domains , and the largest of the variable extensions (V 8 ), are targeted by IgG during infection in vivo . Although the GAS BP show large variations in size and sequence , the modular nature of the pilus proteins revealed by the T 6 structure may aid the future design of a pilus-based vaccine .

Diseases
Validation

Diseases presenting "acute pharyngitis" symptom

acute rheumatic fever

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