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Immunoglobulin‐like domains of the cargo proteins are essential for protein stability during secretion by the type IX secretion system
Author(s) -
Sato Keiko,
Kakuda Shinji,
Yukitake Hideharu,
Kondo Yoshio,
Shoji Mikio,
Takebe Katsuki,
Narita Yuka,
Naito Mariko,
Nakane Daisuke,
Abiko Yoshimitsu,
Hiratsuka Koichi,
Suzuki Mamoru,
Nakayama Koji
Publication year - 2018
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.14083
Subject(s) - biology , secretion , porphyromonas gingivalis , proteases , immunoglobulin domain , microbiology and biotechnology , thioredoxin , biochemistry , receptor , genetics , enzyme , bacteria
Summary The periodontal pathogen Porphyromonas gingivalis secretes many potent virulence factors using the type IX secretion system (T9SS). T9SS cargo proteins that have been structurally determined by X‐ray crystallography are composed of a signal peptide, functional domain(s), an immunoglobulin (Ig)‐like domain and a C‐terminal domain. Role of the Ig‐like domains of cargo proteins in the T9SS has not been elucidated. Gingipain proteases, which are cargo proteins of the T9SS, were degraded when their Ig‐like domains were lacking or truncated. The degradation was dependent on the activity of a quality control factor, HtrA protease. Another T9SS cargo protein, HBP35, which has a thioredoxin domain as a functional domain, was analyzed by X‐ray crystallography, revealing that HBP35 has an Ig‐like domain after the thioredoxin domain and that the hydrophobic regions of the thioredoxin domain and the Ig‐like domain face each other. HBP35 with substitution of hydrophobic amino acids in the Ig‐like domain was degraded depending on HtrA. These results suggest that the Ig‐like domain mediates stability of the cargo proteins in the T9SS.