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High-resolution structure of a type IV pilin from the metal-reducing bacterium Shewanella oneidensis.

Gorgel M, Ulstrup JJ, Bøggild A, Jones NC, Hoffmann SV, Nissen P, Boesen T - BMC Struct. Biol. (2015)

Bottom Line: Interestingly, our PilBac1 crystal structure reveals two unusual features compared to other type IVa pilins: an unusual position of the disulfide bridge and a straight α-helical section, which usually exhibits a pronounced kink.In this study we have described the first structure of a pilin from Shewanella oneidensis.The structure possesses features of the common type IV pilin core, but also exhibits significant variations in the α-helical part and the D-region.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus C, 8000, Denmark. manuela@mbg.au.dk.

ABSTRACT

Background: Type IV pili are widely expressed among Gram-negative bacteria, where they are involved in biofilm formation, serve in the transfer of DNA, motility and in the bacterial attachment to various surfaces. Type IV pili in Shewanella oneidensis are also supposed to play an important role in extracellular electron transfer by the attachment to sediments containing electron acceptors and potentially forming conductive nanowires.

Results: The potential nanowire type IV pilin PilBac1 from S. oneidensis was characterized by a combination of complementary structural methods and the atomic structure was determined at a resolution of 1.67 Å by X-ray crystallography. PilBac1 consists of one long N-terminal α-helix packed against four antiparallel β-strands, thus revealing the core fold of type IV pilins. In the crystal, PilBac1 forms a parallel dimer with a sodium ion bound to one of the monomers. Interestingly, our PilBac1 crystal structure reveals two unusual features compared to other type IVa pilins: an unusual position of the disulfide bridge and a straight α-helical section, which usually exhibits a pronounced kink. This straight helix leads to a distinct packing in a filament model of PilBac1 based on an EM model of a Neisseria pilus.

Conclusions: In this study we have described the first structure of a pilin from Shewanella oneidensis. The structure possesses features of the common type IV pilin core, but also exhibits significant variations in the α-helical part and the D-region.

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Dimer of PilBac1ΔN. A: Dimeric interface between two PilBac1∆N molecules in the crystal. B: Superposition of a PilBac1∆N monomer with PilE from N. gonorrhoeae (2HI2.PDB). C: Superposition based on the head domains of a PilBac1∆N monomer with the modelled α-helix onto PilE from N. gonorrhoeae (2HI2.PDB). D: PilBac1∆N dimer with the modelled α-helices at the N-terminus based on a superposition with the α-helix from PilE from N. gonorrhoeae (2HI2.PDB). E: Potential arrangement of a PilBac1 dimer in a membrane. This figure was generated with the PPM server [79]. The structure of PilBac1∆N is shown in blue, the modelled helix in cyan and PilE from N. gonorrhoeae is shown in red.
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Fig5: Dimer of PilBac1ΔN. A: Dimeric interface between two PilBac1∆N molecules in the crystal. B: Superposition of a PilBac1∆N monomer with PilE from N. gonorrhoeae (2HI2.PDB). C: Superposition based on the head domains of a PilBac1∆N monomer with the modelled α-helix onto PilE from N. gonorrhoeae (2HI2.PDB). D: PilBac1∆N dimer with the modelled α-helices at the N-terminus based on a superposition with the α-helix from PilE from N. gonorrhoeae (2HI2.PDB). E: Potential arrangement of a PilBac1 dimer in a membrane. This figure was generated with the PPM server [79]. The structure of PilBac1∆N is shown in blue, the modelled helix in cyan and PilE from N. gonorrhoeae is shown in red.

Mentions: PilBac1ΔN was crystallized as a parallel dimer in the asymmetric unit in which the interface is formed by interactions between 15 and 20 residues in the α-helix from monomers A and B, respectively (forming a non-proper dimer with a screw-axis) (R.M.S.D. of 0.309 Å based on 79 out of a total of 89 Cαs)(Figure 5A). Previously it was noted that pilins can exist as dimers and multimers [71-73]. Many structures of type IV pilins and pseudopilins were also determined in a dimeric [32,68,74-78] or even in a trimeric state [68]. However, different to PilBac1ΔN, most of them were not arranged in a physiologically relevant conformation (e.g. antiparallel, in-line). The structures of the T4P CofA from E. coli (3S0T.PDB) and of the pseudopilin PulG from E. coli (3G20.PDB) were determined as dimers, in which the monomers are further apart from each other. This dimerization was probably caused by crystal contacts. In contrast, in the structure of full-length FimA from D. nodosus, the two monomers are held together by extensive, intermolecular interactions. However, unlike PilBac1ΔN, the dimeric interface is here formed between the transmembrane domains.Figure 5


High-resolution structure of a type IV pilin from the metal-reducing bacterium Shewanella oneidensis.

Gorgel M, Ulstrup JJ, Bøggild A, Jones NC, Hoffmann SV, Nissen P, Boesen T - BMC Struct. Biol. (2015)

Dimer of PilBac1ΔN. A: Dimeric interface between two PilBac1∆N molecules in the crystal. B: Superposition of a PilBac1∆N monomer with PilE from N. gonorrhoeae (2HI2.PDB). C: Superposition based on the head domains of a PilBac1∆N monomer with the modelled α-helix onto PilE from N. gonorrhoeae (2HI2.PDB). D: PilBac1∆N dimer with the modelled α-helices at the N-terminus based on a superposition with the α-helix from PilE from N. gonorrhoeae (2HI2.PDB). E: Potential arrangement of a PilBac1 dimer in a membrane. This figure was generated with the PPM server [79]. The structure of PilBac1∆N is shown in blue, the modelled helix in cyan and PilE from N. gonorrhoeae is shown in red.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4376143&req=5

Fig5: Dimer of PilBac1ΔN. A: Dimeric interface between two PilBac1∆N molecules in the crystal. B: Superposition of a PilBac1∆N monomer with PilE from N. gonorrhoeae (2HI2.PDB). C: Superposition based on the head domains of a PilBac1∆N monomer with the modelled α-helix onto PilE from N. gonorrhoeae (2HI2.PDB). D: PilBac1∆N dimer with the modelled α-helices at the N-terminus based on a superposition with the α-helix from PilE from N. gonorrhoeae (2HI2.PDB). E: Potential arrangement of a PilBac1 dimer in a membrane. This figure was generated with the PPM server [79]. The structure of PilBac1∆N is shown in blue, the modelled helix in cyan and PilE from N. gonorrhoeae is shown in red.
Mentions: PilBac1ΔN was crystallized as a parallel dimer in the asymmetric unit in which the interface is formed by interactions between 15 and 20 residues in the α-helix from monomers A and B, respectively (forming a non-proper dimer with a screw-axis) (R.M.S.D. of 0.309 Å based on 79 out of a total of 89 Cαs)(Figure 5A). Previously it was noted that pilins can exist as dimers and multimers [71-73]. Many structures of type IV pilins and pseudopilins were also determined in a dimeric [32,68,74-78] or even in a trimeric state [68]. However, different to PilBac1ΔN, most of them were not arranged in a physiologically relevant conformation (e.g. antiparallel, in-line). The structures of the T4P CofA from E. coli (3S0T.PDB) and of the pseudopilin PulG from E. coli (3G20.PDB) were determined as dimers, in which the monomers are further apart from each other. This dimerization was probably caused by crystal contacts. In contrast, in the structure of full-length FimA from D. nodosus, the two monomers are held together by extensive, intermolecular interactions. However, unlike PilBac1ΔN, the dimeric interface is here formed between the transmembrane domains.Figure 5

Bottom Line: Interestingly, our PilBac1 crystal structure reveals two unusual features compared to other type IVa pilins: an unusual position of the disulfide bridge and a straight α-helical section, which usually exhibits a pronounced kink.In this study we have described the first structure of a pilin from Shewanella oneidensis.The structure possesses features of the common type IV pilin core, but also exhibits significant variations in the α-helical part and the D-region.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus C, 8000, Denmark. manuela@mbg.au.dk.

ABSTRACT

Background: Type IV pili are widely expressed among Gram-negative bacteria, where they are involved in biofilm formation, serve in the transfer of DNA, motility and in the bacterial attachment to various surfaces. Type IV pili in Shewanella oneidensis are also supposed to play an important role in extracellular electron transfer by the attachment to sediments containing electron acceptors and potentially forming conductive nanowires.

Results: The potential nanowire type IV pilin PilBac1 from S. oneidensis was characterized by a combination of complementary structural methods and the atomic structure was determined at a resolution of 1.67 Å by X-ray crystallography. PilBac1 consists of one long N-terminal α-helix packed against four antiparallel β-strands, thus revealing the core fold of type IV pilins. In the crystal, PilBac1 forms a parallel dimer with a sodium ion bound to one of the monomers. Interestingly, our PilBac1 crystal structure reveals two unusual features compared to other type IVa pilins: an unusual position of the disulfide bridge and a straight α-helical section, which usually exhibits a pronounced kink. This straight helix leads to a distinct packing in a filament model of PilBac1 based on an EM model of a Neisseria pilus.

Conclusions: In this study we have described the first structure of a pilin from Shewanella oneidensis. The structure possesses features of the common type IV pilin core, but also exhibits significant variations in the α-helical part and the D-region.

Show MeSH
Related in: MedlinePlus