Correlation of the amino-acid sequence and the 3D structure of the functional domain of EmaA from Aggregatibacter actinomycetemcomitans

Azari, Fereshteh; Radermacher, Michael; Mintz, Keith P.; Ruíz, Teresa

doi:10.1016/j.jsb.2011.11.024

Cited by 15 publications

(44 citation statements)

References 38 publications

(67 reference statements)

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“…EmaA molecules assemble into antenna-like appendages on the surface of the bacterium and specifically bind to collagen (16,25,32). It has also been proposed that collagen interacts with the head domain of EmaA, which correspond to the N termini of the proteins, or the globular ends of the antenna-like cell surface appendages (1,36). The EmaA structures, which extend at least 150 nm from the surface, have been implicated in the initiation of infective endocarditis (31).…”

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confidence: 99%

O-Polysaccharide Glycosylation Is Required for Stability and Function of the Collagen Adhesin EmaA of Aggregatibacter actinomycetemcomitans

2012

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confidence: 99%

O-Polysaccharide Glycosylation Is Required for Stability and Function of the Collagen Adhesin EmaA of Aggregatibacter actinomycetemcomitans

2012

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“…1D). Images of the wild-type strain show grooves on the bacterial surface and also the presence of the collagen binding adhesin, extracellular matrix adhesin A (EmaA), that forms antenna-like structures protruding from the bacterial surface (13,22,30,31). Our earlier studies revealed that convolutions in A. actinomycetemcomitans are associated with a protein called morphogenesis protein C (MorC), which appears to be located in the inner membrane (29).…”

Section: Resultsmentioning

confidence: 99%

“…However, the loss of the rugosity does not seem to influence the presentation of all virulence determinants on the outer bacterial surface. EmaA (extracellular matrix adhesin A), a trimeric autotransporter collagen binding adhesin that forms antenna-like appendages on the surface of the bacterium (13,22,30,31), is present in both wild-type and morC mutant strains, thus indicating that not all outer membrane transport systems are affected. All of these observations raise fundamental questions about the specific role of the outer membrane morphology and the spatial relationship between outer and inner membranes in bacteria with a native rugose phenotype.…”

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Ultrastructural Analysis of the Rugose Cell Envelope of a Member of the Pasteurellaceae Family

Azari

Nyland

et al. 2013

J Bacteriol

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Bacterial membranes serve as selective environmental barriers and contain determinants required for bacterial colonization and survival. Cell envelopes of Gram-negative bacteria consist of an outer and an inner membrane separated by a periplasmic space. Most Gram-negative bacteria display a smooth outer surface (e.g., Enterobacteriaceae), whereas members of the Pasteurellaceae and Moraxellaceae families show convoluted surfaces. Aggregatibacter actinomycetemcomitans, an oral pathogen representative of the Pasteurellaceae family, displays a convoluted membrane morphology. This phenotype is associated with the presence of morphogenesis protein C (MorC). Inactivation of the morC gene results in a smooth membrane appearance when visualized by two-dimensional (2D) electron microscopy. In this study, 3D electron microscopy and atomic force microscopy of whole-mount bacterial preparations as well as 3D electron microscopy of ultrathin sections of high-pressure frozen and freeze-substituted specimens were used to characterize the membranes of both wildtype and morC mutant strains of A. actinomycetemcomitans. Our results show that the mutant strain contains fewer convolutions than the wild-type bacterium, which exhibits a higher curvature of the outer membrane and a periplasmic space with 2-fold larger volume/area ratio than the mutant bacterium. The inner membrane of both strains has a smooth appearance and shows connections with the outer membrane, as revealed by visualization and segmentation of 3D tomograms. The present studies and the availability of genetically modified organisms with altered outer membrane morphology make A. actinomycetemcomitans a model organism for examining membrane remodeling and its implications in antibiotic resistance and virulence in the Pasteurellaceae and Moraxellaceae bacterial families.

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“…EmaA adhesins from a serotype b strain were analyzed by electron tomography of whole-mount negatively-stained preparations of the bacteria (Fig 2.a) [3]. Tomographic single-axis tilt series over a ±64° angular range in 2° intervals were acquired with a calibrated pixelsize at the specimen scale of 0.308 nm.…”

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3D Structural Analysis and Classification of EmaA, a Collagen Binding Adhesin

et al. 2017

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Periodontal diseases represent a group of inflammatory conditions that lead to the destruction of periodontal tissues and are the most common cause of tooth loss in American adults. Aggregatibacter actinomycetemcomitans is associated with both the chronic and localized aggressive forms of periodontal diseases, as well as with infective endocarditis and urinary track infections. The binding of this Gram-negative bacterium to the host extracellular matrix collagen is mediated by the surface adhesin EmaA (extracellular matrix protein adhesin A), a virulence determinant ubiquitous in all A. actinomycetemcomitans serotypes. EmaA is one of the largest members of the trimeric autotransporter family with a monomer of 202 kDa in molecular mass. The C-terminal regions of three EmaA monomers create a pore for translocation of the three N-terminal passenger domains across the outer membrane. These domains form antennae-like structures that project more than 150 nm away from the bacterial surface. The 760 N-terminal amino acids of the EmaA monomers comprise the functional domain of the adhesin ( Fig. 1) and are localized at the distal end of the appendage, within the most distal 30 nm [1]. The functional domain is further divided into three subdomains: SI-SIII, with SII and SIII separated by a linker region of 3 nm in diameter comprising a three α-helix coiled-coil. Moreover, EmaA glycosylation was shown to be essential for its structural stability and collagen-binding ability [2]. To date, a high resolution structure of EmaA is lacking and the predictions from structural modeling programs are not compatible with available structural data. Thus, it is necessary to achieve a more detailed map of the secondary/tertiary/quaternary structure of the functional domain of EmaA.EmaA adhesins from a serotype b strain were analyzed by electron tomography of whole-mount negatively-stained preparations of the bacteria (Fig 2.a) [3]. Tomographic single-axis tilt series over a ±64° angular range in 2° intervals were acquired with a calibrated pixelsize at the specimen scale of 0.308 nm. The tilt series were processed using IMOD to generate tomograms. EmaA adhesins were selected from the tomograms by marking two points on their axis. For each selected adhesin, a tilt series of subprojections was extracted and subvolumes were calculated with the adhesin's axis approximately parallel to the Y-axis using algorithms in EMIRA [4]. The adhesin subvolumes were rotationally aligned to a preliminary 3-fold symmetrized averaged reference [1] by projection-based 3D volume alignment [5]. The calculated rotation was applied to the subprojections and translational shifts of the subvolumes were calculated by real space cross correlation. The aligned EmaA subvolumes underwent principle component analysis with expectation maximization (PPCA-EM) [6]. Outliers (with sigma of 5) were identified and excluded from this stage of the analysis. The PPCA-EM data was clustered using Diday's method of moving centers and representative 3D group averages were calculate...

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Correlation of the amino-acid sequence and the 3D structure of the functional domain of EmaA from Aggregatibacter actinomycetemcomitans

Cited by 15 publications

References 38 publications

O-Polysaccharide Glycosylation Is Required for Stability and Function of the Collagen Adhesin EmaA of Aggregatibacter actinomycetemcomitans

O-Polysaccharide Glycosylation Is Required for Stability and Function of the Collagen Adhesin EmaA of Aggregatibacter actinomycetemcomitans

Ultrastructural Analysis of the Rugose Cell Envelope of a Member of the Pasteurellaceae Family

3D Structural Analysis and Classification of EmaA, a Collagen Binding Adhesin

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