title: Crystal structure of the Haemophilus influenzae Hap adhesin reveals an intercellular oligomerization mechanism for bacterial aggregation.
abstract: Bacterial biofilms are complex microbial communities that are common in nature and are being recognized increasingly as an important determinant of bacterial virulence. However, the structural determinants of bacterial aggregation and eventual biofilm formation have been poorly defined. In Gram-negative bacteria, a major subgroup of extracellular proteins called self-associating autotransporters (SAATs) can mediate cell-cell adhesion and facilitate biofilm formation. In this study, we used the Haemophilus influenzae Hap autotransporter as a prototype SAAT to understand how bacteria associate with each other. The crystal structure of the H. influenzae Hap(S) passenger domain (harbouring the SAAT domain) was determined to 2.2 Å by X-ray crystallography, revealing an unprecedented intercellular oligomerization mechanism for cell-cell interaction. The C-terminal SAAT domain folds into a triangular-prism-like structure that can mediate Hap-Hap dimerization and higher degrees of multimerization through its F1-F2 edge and F2 face. The intercellular multimerization can give rise to massive buried surfaces that are required for overcoming the repulsive force between cells, leading to bacterial cell-cell interaction and formation of complex microcolonies.
authors.affiliation: State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital affiliated to Shanghai JiaoTong University School of Medicine, PR China. guoyumeng@shsmu.edu.cn
authors.forename: Guoyu
authors.initials: G
authors.lastname: Meng
authors.forename: Nicole
authors.initials: N
authors.lastname: Spahich
authors.forename: Roma
authors.initials: R
authors.lastname: Kenjale
authors.forename: Gabriel
authors.initials: G
authors.lastname: Waksman
authors.forename: Joseph W
authors.initials: JW
authors.lastname: St Geme
mesh_terms: D001422:Bacterial Adhesion; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D006193:Haemophilus influenzae / Q000737:chemistry*; D008954:Models, Biological; D008958:Models, Molecular; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; C091552:Hap protein, Hemophilus influenzae; D012697:Serine Endopeptidases