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The TPR domain of BepA is required for productive interaction with substrate proteins and the β‐barrel assembly machinery complex
Author(s) -
Daimon Yasushi,
IwamaMasui Chigusa,
Tanaka Yoshiki,
Shiota Takuya,
Suzuki Takehiro,
Miyazaki Ryoji,
Sakurada Hiroto,
Lithgow Trevor,
Dohmae Naoshi,
Mori Hiroyuki,
Tsukazaki Tomoya,
Narita Shinichiro,
Akiyama Yoshinori
Publication year - 2017
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.13844
Subject(s) - tetratricopeptide , bacterial outer membrane , biology , biogenesis , periplasmic space , chaperone (clinical) , microbiology and biotechnology , protease , translocon , transport protein , protein domain , protein folding , biophysics , biochemistry , membrane protein , membrane , escherichia coli , enzyme , medicine , pathology , gene
Summary BepA (formerly YfgC) is an Escherichia coli periplasmic protein consisting of an N‐terminal protease domain and a C‐terminal tetratricopeptide repeat (TPR) domain. We have previously shown that BepA is a dual functional protein with chaperone‐like and proteolytic activities involved in membrane assembly and proteolytic quality control of LptD, a major component of the outer membrane lipopolysaccharide translocon. Intriguingly, BepA can associate with the BAM complex: the β‐barrel assembly machinery (BAM) driving integration of β‐barrel proteins into the outer membrane. However, the molecular mechanism of BepA function and its association with the BAM complex remains unclear. Here, we determined the crystal structure of the BepA TPR domain, which revealed the presence of two subdomains formed by four TPR motifs. Systematic site‐directed in vivo photo‐cross‐linking was used to map the protein–protein interactions mediated by the BepA TPR domain, showing that this domain interacts both with a substrate and with the BAM complex. Mutational analysis indicated that these interactions are important for the BepA functions. These results suggest that the TPR domain plays critical roles in BepA functions through interactions both with substrates and with the BAM complex. Our findings provide insights into the mechanism of biogenesis and quality control of the outer membrane.