5AX6

The crystal structure of CofB, the minor pilin subunit of CFA/III from human enterotoxigenic Escherichia coli.

Summary for 5AX6

• Entry DOI: 10.2210/pdb5ax6/pdb
• Descriptor: CofB, ACETATE ION (3 entities in total)
• Functional Keywords: minor pilin, cell adhesion
• Biological source: Escherichia coli
• Total number of polymer chains: 1
• Total formula weight: 53652.49

Authors

Kawahara, K.,Oki, K.,Fukaksua, F.,Maruno, T.,Kobayashi, Y.,Daisuke, M.,Taniguchi, T.,Honda, T.,Iida, T.,Nakamura, S.,Ohkubo, T. (deposition date: 2015-07-16, release date: 2016-03-09, Last modification date: 2024-11-13)

Primary citation

Kawahara, K.,Oki, H.,Fukakusa, S.,Yoshida, T.,Imai, T.,Maruno, T.,Kobayashi, Y.,Motooka, D.,Iida, T.,Ohkubo, T.,Nakamura, S.
Homo-trimeric Structure of the Type IVb Minor Pilin CofB Suggests Mechanism of CFA/III Pilus Assembly in Human Enterotoxigenic Escherichia coli
J.Mol.Biol., 428:1209-1226, 2016

PubMed Abstract: In gram-negative bacteria, the assembly of type IV pilus (T4P) and the evolutionally related pseudopilus of type II secretion system involves specialized structural proteins called pilins and pseudopilins, respectively, and is dynamically regulated to promote bacterial pathogenesis. Previous studies have suggested that a structural "tip"-like hetero-complex formed through the interaction of at least three minor (pseudo) pilins plays an important role in this process, while some members of the pathogenic type IVb subfamily are known to have only one such minor pilin subunit whose function is still unknown. Here, we determined the crystal structure of the type IVb minor pilin CofB of colonization factor antigen/III from human enterotoxigenic Escherichia coli at 1.88-Å resolution. The crystal structure, in conjunction with physicochemical analysis in solution, reveals a symmetrical homo-trimeric arrangement distinct from the hetero-complexes of minor (pseudo) pilins observed in other T4P and type II secretion systems. Each CofB monomer adopts a unique three-domain architecture, in which the C-terminal β-sheet-rich lectin domain can effectively initiate trimer association of its pilin-like N-terminal domain through extensive hydrophobic interactions followed by domain swapping at the central hinge-like domain. Deletion of cofB produces a phenotype with no detectable pili formation on the cell surface, while molecular modeling indicates that the characteristic homo-trimeric structure of CofB is well situated at the pilus tip of colonization factor antigen/III formed by the major pilin CofA, suggesting a role for the minor pilin in the efficient initiation of T4P assembly.

PubMed: 26876601
DOI: 10.1016/j.jmb.2016.02.003

Experimental method

X-RAY DIFFRACTION (1.88 Å)