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Repetitive architecture of the Haemophilus influenzae Hia trimeric autotransporter.

Meng G, St Geme JW, Waksman G - J. Mol. Biol. (2008)

Bottom Line: Comparison of the structures of HiaBD1 and HiaBD2 adhesive repeats and a nonadhesive repeat (a novel fold) shed light on the structural determinants of Hia adhesive function.Examination of the structure of an extended version of the Hia translocator domain revealed the structural transition between the C-terminal translocator domain and the N-terminal passenger domain, highlighting a highly intertwined domain that is ubiquitous among trimeric autotransporters.Overall, this study provides important insights into the mechanism of Hia adhesive activity and the overall structure of trimeric autotransporters.

View Article: PubMed Central - PubMed

Affiliation: Institute of Structural and Molecular Biology at UCL/Birkbeck, London, UK.

ABSTRACT
The Hia autotransporter of Haemophilus influenzae belongs to the trimeric autotransporter subfamily and mediates bacterial adherence to the respiratory epithelium. In this report, we show that the structure of Hia is characterized by a modular architecture containing repeats of structurally distinct domains. Comparison of the structures of HiaBD1 and HiaBD2 adhesive repeats and a nonadhesive repeat (a novel fold) shed light on the structural determinants of Hia adhesive function. Examination of the structure of an extended version of the Hia translocator domain revealed the structural transition between the C-terminal translocator domain and the N-terminal passenger domain, highlighting a highly intertwined domain that is ubiquitous among trimeric autotransporters. Overall, this study provides important insights into the mechanism of Hia adhesive activity and the overall structure of trimeric autotransporters.

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Structures of the Hia51–166 and Hia307–422 monomers and trimers. (a) Stereo ribbon diagram of the Hia51–166monomer. Secondary structures, including helices and strands, are labeled. (b) Stereo ribbon diagram of the Hia51–166 trimer. The three subunits are shown in magenta, yellow, and orange. (c) Stereo ribbon diagram of the Hia307–422 monomer. Secondary structures, including helices and strands, are labeled. (d) Stereo ribbon diagram of the Hia307–422 trimer. The three subunits are shown in the same color scheme as mentioned above.
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fig2: Structures of the Hia51–166 and Hia307–422 monomers and trimers. (a) Stereo ribbon diagram of the Hia51–166monomer. Secondary structures, including helices and strands, are labeled. (b) Stereo ribbon diagram of the Hia51–166 trimer. The three subunits are shown in magenta, yellow, and orange. (c) Stereo ribbon diagram of the Hia307–422 monomer. Secondary structures, including helices and strands, are labeled. (d) Stereo ribbon diagram of the Hia307–422 trimer. The three subunits are shown in the same color scheme as mentioned above.

Mentions: The structure of HiaBD2 was determined to a resolution of 2.0 Å, using molecular replacement and HiaBD1 as search model (Tables 1 and 2; Supplementary Fig. 1). HiaBD2 contains two well-defined structural domains, namely, IN1 and W1. IN1 is a globular knob-like domain with a simple α/β sandwich fold. Two short β-strands (βIN11 and βIN12) form a short β-sheet, flanked by four helices: αIN11–αIN13 on one side and αIN14 on the other side (Fig. 2a). In the trimer, αIN14 from each HiaBD2 subunit forms a three-helix bundle parallel with the axis of the trimer from which the three knob-like shapes protrude laterally (Fig. 2b). The W1 domain of HiaBD2 is an all-β domain consisting of five long β-strands (βW11–βW15; Fig. 2a). In the monomer, these strands—including two β-hairpins (βW11–βW12 and βW14–βW15) and a connector strand (βW13)—are remarkably segregated and twisted into an N-shape (Fig. 2a). In the trimer, these strands are highly intertwined, forming a five-stranded β-sheet on each face of the trimer and serving as a surface against which the αIN12 and αIN13 helices of IN1 rest (Fig. 2b). The structures of HiaBD2 and HiaBD1 are very similar, aligning with a root mean square deviation (RMSD) in Cα positions of 1.1 Å between IN1 of HiaBD2 and IN2 of HiaBD1, and 1.5 Å between W1 of HiaBD2 and W5 of HiaBD1 (see superposition of the two structures in Fig. 3a).


Repetitive architecture of the Haemophilus influenzae Hia trimeric autotransporter.

Meng G, St Geme JW, Waksman G - J. Mol. Biol. (2008)

Structures of the Hia51–166 and Hia307–422 monomers and trimers. (a) Stereo ribbon diagram of the Hia51–166monomer. Secondary structures, including helices and strands, are labeled. (b) Stereo ribbon diagram of the Hia51–166 trimer. The three subunits are shown in magenta, yellow, and orange. (c) Stereo ribbon diagram of the Hia307–422 monomer. Secondary structures, including helices and strands, are labeled. (d) Stereo ribbon diagram of the Hia307–422 trimer. The three subunits are shown in the same color scheme as mentioned above.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2597055&req=5

fig2: Structures of the Hia51–166 and Hia307–422 monomers and trimers. (a) Stereo ribbon diagram of the Hia51–166monomer. Secondary structures, including helices and strands, are labeled. (b) Stereo ribbon diagram of the Hia51–166 trimer. The three subunits are shown in magenta, yellow, and orange. (c) Stereo ribbon diagram of the Hia307–422 monomer. Secondary structures, including helices and strands, are labeled. (d) Stereo ribbon diagram of the Hia307–422 trimer. The three subunits are shown in the same color scheme as mentioned above.
Mentions: The structure of HiaBD2 was determined to a resolution of 2.0 Å, using molecular replacement and HiaBD1 as search model (Tables 1 and 2; Supplementary Fig. 1). HiaBD2 contains two well-defined structural domains, namely, IN1 and W1. IN1 is a globular knob-like domain with a simple α/β sandwich fold. Two short β-strands (βIN11 and βIN12) form a short β-sheet, flanked by four helices: αIN11–αIN13 on one side and αIN14 on the other side (Fig. 2a). In the trimer, αIN14 from each HiaBD2 subunit forms a three-helix bundle parallel with the axis of the trimer from which the three knob-like shapes protrude laterally (Fig. 2b). The W1 domain of HiaBD2 is an all-β domain consisting of five long β-strands (βW11–βW15; Fig. 2a). In the monomer, these strands—including two β-hairpins (βW11–βW12 and βW14–βW15) and a connector strand (βW13)—are remarkably segregated and twisted into an N-shape (Fig. 2a). In the trimer, these strands are highly intertwined, forming a five-stranded β-sheet on each face of the trimer and serving as a surface against which the αIN12 and αIN13 helices of IN1 rest (Fig. 2b). The structures of HiaBD2 and HiaBD1 are very similar, aligning with a root mean square deviation (RMSD) in Cα positions of 1.1 Å between IN1 of HiaBD2 and IN2 of HiaBD1, and 1.5 Å between W1 of HiaBD2 and W5 of HiaBD1 (see superposition of the two structures in Fig. 3a).

Bottom Line: Comparison of the structures of HiaBD1 and HiaBD2 adhesive repeats and a nonadhesive repeat (a novel fold) shed light on the structural determinants of Hia adhesive function.Examination of the structure of an extended version of the Hia translocator domain revealed the structural transition between the C-terminal translocator domain and the N-terminal passenger domain, highlighting a highly intertwined domain that is ubiquitous among trimeric autotransporters.Overall, this study provides important insights into the mechanism of Hia adhesive activity and the overall structure of trimeric autotransporters.

View Article: PubMed Central - PubMed

Affiliation: Institute of Structural and Molecular Biology at UCL/Birkbeck, London, UK.

ABSTRACT
The Hia autotransporter of Haemophilus influenzae belongs to the trimeric autotransporter subfamily and mediates bacterial adherence to the respiratory epithelium. In this report, we show that the structure of Hia is characterized by a modular architecture containing repeats of structurally distinct domains. Comparison of the structures of HiaBD1 and HiaBD2 adhesive repeats and a nonadhesive repeat (a novel fold) shed light on the structural determinants of Hia adhesive function. Examination of the structure of an extended version of the Hia translocator domain revealed the structural transition between the C-terminal translocator domain and the N-terminal passenger domain, highlighting a highly intertwined domain that is ubiquitous among trimeric autotransporters. Overall, this study provides important insights into the mechanism of Hia adhesive activity and the overall structure of trimeric autotransporters.

Show MeSH
Related in: MedlinePlus