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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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Structure comparison between adhesive domains HiaBD1 and HiaBD2 and the nonadhesive domain Hia307–422. (a) Stereo ribbon diagram of the superimposed HiaBD1 (red) and HiaBD2 (blue) domains. (b) Stereo ribbon diagram of the superimposed HiaBD1 (red) and Hia307–422 (green) domains. (c) Detailed molecular feature of the groove formed by the base of the IN domain (αIN2 and αIN3) and the top of the adjacent W domain (βW1 and βW3). Mutations of residues D618 (in the loop between αIN2 and αIN3), A620 (in αIN3), and V656 (in βW1) all abolished the adhesion activities of HiaBD1 in vivo and in vitro. (d) Ribbon diagram of the superimposed IN2 (red) and KG1 (green) domains. The helices, including αKG1, αKG2, and αKG3 in KG domain and αIN2, αIN1, and αIN4 in IN domain, are labeled respectively. (e) Sequence alignment of the IN and W adhesive-like domains among Hia/Hsf adhesins. (⁎) Invariant residues. The three functional important residues are highlighted in blue. (f) Sequence alignment of the KG domains between Hia/Hsf/NhhA.
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fig3: Structure comparison between adhesive domains HiaBD1 and HiaBD2 and the nonadhesive domain Hia307–422. (a) Stereo ribbon diagram of the superimposed HiaBD1 (red) and HiaBD2 (blue) domains. (b) Stereo ribbon diagram of the superimposed HiaBD1 (red) and Hia307–422 (green) domains. (c) Detailed molecular feature of the groove formed by the base of the IN domain (αIN2 and αIN3) and the top of the adjacent W domain (βW1 and βW3). Mutations of residues D618 (in the loop between αIN2 and αIN3), A620 (in αIN3), and V656 (in βW1) all abolished the adhesion activities of HiaBD1 in vivo and in vitro. (d) Ribbon diagram of the superimposed IN2 (red) and KG1 (green) domains. The helices, including αKG1, αKG2, and αKG3 in KG domain and αIN2, αIN1, and αIN4 in IN domain, are labeled respectively. (e) Sequence alignment of the IN and W adhesive-like domains among Hia/Hsf adhesins. (⁎) Invariant residues. The three functional important residues are highlighted in blue. (f) Sequence alignment of the KG domains between Hia/Hsf/NhhA.

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)

Structure comparison between adhesive domains HiaBD1 and HiaBD2 and the nonadhesive domain Hia307–422. (a) Stereo ribbon diagram of the superimposed HiaBD1 (red) and HiaBD2 (blue) domains. (b) Stereo ribbon diagram of the superimposed HiaBD1 (red) and Hia307–422 (green) domains. (c) Detailed molecular feature of the groove formed by the base of the IN domain (αIN2 and αIN3) and the top of the adjacent W domain (βW1 and βW3). Mutations of residues D618 (in the loop between αIN2 and αIN3), A620 (in αIN3), and V656 (in βW1) all abolished the adhesion activities of HiaBD1 in vivo and in vitro. (d) Ribbon diagram of the superimposed IN2 (red) and KG1 (green) domains. The helices, including αKG1, αKG2, and αKG3 in KG domain and αIN2, αIN1, and αIN4 in IN domain, are labeled respectively. (e) Sequence alignment of the IN and W adhesive-like domains among Hia/Hsf adhesins. (⁎) Invariant residues. The three functional important residues are highlighted in blue. (f) Sequence alignment of the KG domains between Hia/Hsf/NhhA.
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fig3: Structure comparison between adhesive domains HiaBD1 and HiaBD2 and the nonadhesive domain Hia307–422. (a) Stereo ribbon diagram of the superimposed HiaBD1 (red) and HiaBD2 (blue) domains. (b) Stereo ribbon diagram of the superimposed HiaBD1 (red) and Hia307–422 (green) domains. (c) Detailed molecular feature of the groove formed by the base of the IN domain (αIN2 and αIN3) and the top of the adjacent W domain (βW1 and βW3). Mutations of residues D618 (in the loop between αIN2 and αIN3), A620 (in αIN3), and V656 (in βW1) all abolished the adhesion activities of HiaBD1 in vivo and in vitro. (d) Ribbon diagram of the superimposed IN2 (red) and KG1 (green) domains. The helices, including αKG1, αKG2, and αKG3 in KG domain and αIN2, αIN1, and αIN4 in IN domain, are labeled respectively. (e) Sequence alignment of the IN and W adhesive-like domains among Hia/Hsf adhesins. (⁎) Invariant residues. The three functional important residues are highlighted in blue. (f) Sequence alignment of the KG domains between Hia/Hsf/NhhA.
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