Open AccessInvestigation of the Three-Dimensional Architecture of the Collagen Adhesin EmaA ofAggregatibacter actinomycetemcomitansby Electron Tomography
Author(s) -
Chenggang Yu,
Keith P. Mintz,
Teresa Ruíz
Publication year - 2009
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.00563-09
Subject(s) - biology , bacterial adhesin , aggregatibacter actinomycetemcomitans , cryo electron tomography , microbiology and biotechnology , electron tomography , tomography , bacteria , biochemistry , electron microscope , genetics , virulence , optics , gene , physics , porphyromonas gingivalis , scanning transmission electron microscopy
The periodontal pathogenAggregatibacter actinomycetemcomitans displays on the bacterial surface a nonfimbrial adhesin, EmaA, which is required for collagen binding. In this study, electron tomography was used to characterize the three-dimensional (3D) architecture of this adhesin. The antenna-like surface appendages, corresponding to EmaA, were found to be composed of an ellipsoidal domain capping a rod-like domain that adopts either a straight or a bent conformation at various positions along the length. The most common flexible point along the length of the EmaA appendage was localized 29.4 nm away from the distal end. One-fifth of the appendages were straight and the remaining showed angles distributed between 140° and 170° at this location. Deletion analysis mapped this bend to amino acids 611 to 640 of the protein sequence. The 3D structure of the collagen binding domain of EmaA was generated by alignment and averaging of 9 subvolumes of the adhesin extracted from tomograms. The structure contains three subdomains: a globular structure with a diameter of ∼5 nm and a cylindrical domain (∼4.4 nm by 5.8 nm) separated by a linker region with a diameter of ∼3 nm, followed by a cylindrical domain (∼4.6 nm by 6.6 nm). This is the first 3D structure of a trimeric autotransporter protein ofA. actinomycetemcomitans .