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Structure of the outer membrane translocator domain of the Haemophilus influenzae Hia trimeric autotransporter
Author(s) -
Meng Guoyu,
Suraeeraj K,
St Geme Joseph W,
Waksman Gabriel
Publication year - 2006
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7601132
Subject(s) - biology , bacterial outer membrane , protein subunit , transmembrane domain , haemophilus influenzae , inner membrane , transmembrane protein , biophysics , microbiology and biotechnology , biochemistry , escherichia coli , membrane , gene , antibiotics , receptor
Autotransporter proteins are defined by the ability to drive their own secretion across the bacterial outer membrane. The Hia autotransporter of Haemophilus influenzae belongs to the trimeric autotransporter subfamily and mediates bacterial adhesion to the respiratory epithelium. In this report, we present the crystal structure of the C‐terminal end of Hia, corresponding to the entire Hia translocator domain and part of the passenger domain (residues 992–1098). This domain forms a β‐barrel with 12 transmembrane β‐strands, including four strands from each subunit. The β‐barrel has a central channel of 1.8 nm in diameter that is traversed by three N‐terminal α‐helices, one from each subunit. Mutagenesis studies demonstrate that the transmembrane portion of the three α‐helices and the loop region between the α‐helices and the neighboring β‐strands are essential for stability of the trimeric structure of the translocator domain, and that trimerization of the translocator domain is a prerequisite for translocator activity. Overall, this study provides important insights into the mechanism of translocation in trimeric autotransporters.