Matsumoto, Airi Tokushima University
Fujimoto, Ai Tokushima University
大倉, 一人 Suzuka University of Medical Science
Ikeda, Takuya Tokushima University
Oda, Hiroki Tokushima University
Yokohata, Shuto Tokushima University
Kobayashi, Miho Tokushima University
Takao, Ayuko Tsurumi University
Ohkuni, Hisashi Health Science Research Institute East Japan
Mitis group streptococci
Background: Some strains of Streptococcus mitis exhibit β-hemolysis due to the β-hemolytic activity of cholesterol-dependent cytolysin (CDC). Recently, a gene encoding an atypical lectinolysin-related CDC was found in S. mitis strain Nm-76. However, the product of this gene remains uncharacterized. We aimed to characterize this atypical CDC and its molecular functions and contribution to the pathogenicity of S. mitis strain Nm-76.
Methods: Phylogenetic analysis of the CDC gene was conducted based on the web-deposited information. The molecular characteristics of CDC were investigated using a gene-deletion mutant strain and recombinant proteins expressed in Escherichia coli.
Results: The gene encoding CDC found in Nm-76 and its homolog are distributed among many S. mitis strains. This CDC is phylogenetically different from other previously characterized CDCs, such as S. mitis-derived human platelet aggregation factor (Sm-hPAF)/lectinolysin and mitilysin. Because this CDC possesses an additional N-terminal domain, including a discoidin motif, it was termed discoidinolysin (DLY). In addition to the preferential lysis of human cells, DLY displayed N-terminal domain-dependent facilitation of human erythrocyte aggregation and intercellular associations between human cells.
Conclusion: DLY functions as a hemolysin/cytolysin and erythrocyte aggregation/intercellular association molecule. This dual-function DLY could be an additional virulence factor in S. mitis.
Journal of Oral Microbiology
Informa UK|Taylor & Francis
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