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Infection and Immunity, July 2008, p. 3116-3123, Vol. 76, No. 7
0019-9567/08/$08.00+0     doi:10.1128/IAI.00173-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

The Surface-Exposed Carboxyl Region of Mycoplasma pneumoniae Elongation Factor Tu Interacts with Fibronectin{triangledown}

Sowmya Balasubramanian, T. R. Kannan, and Joel B. Baseman*

Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, MC 7758, San Antonio, Texas 78229-3900

Received 8 February 2008/ Returned for modification 20 March 2008/ Accepted 6 April 2008

Mycoplasma pneumoniae is a bacterial pathogen of the human respiratory tract that causes a wide range of airway diseases as well as extrapulmonary symptoms. It possesses a distinct, differentiated terminal structure, termed the attachment organelle, that mediates adherence to the host respiratory epithelium. Previously, we reported that surface-associated M. pneumoniae elongation factor Tu (EF-Tu, also called MPN665) serves as a fibronectin (Fn)-binding protein, facilitating interactions between mycoplasmas and extracellular matrix. In the present study, we determined that binding of M. pneumoniae EF-Tu to Fn is primarily mediated by the EF-Tu carboxyl region. A 179-amino-acid region spanning the carboxyl terminus (designated EC; amino acids 192 to 394) binds Fn in a dose-dependent manner. Further analysis of carboxyl constructs (ED3 and ED4) and their deletion truncations (ED3.1, ED3.2, and ED4.1) revealed that the carboxyl region possessed two distinct sites with different Fn-binding efficiencies. Immunogold electron microscopy using antibodies raised against recombinant ED3 and ED4 demonstrated the surface accessibility of the EF-Tu carboxyl region. Competitive binding assays using intact radiolabeled mycoplasmas and purified recombinant ED3 and ED4 proteins, along with antibody blocking assays, reinforced the role of the surface-exposed EF-Tu carboxyl region in Fn binding. Alkali and high-salt treatment of mycoplasma membranes and Triton X-114-partitioned mycoplasma fractions confirmed the stable association of EF-Tu within the mycoplasma membrane. These observations highlight the unique, multifaceted, and unpredictable role of the classically defined cytoplasmic protein EF-Tu relative to cellular function, compartmentalization, and topography.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, MC 7758, San Antonio, TX 78229-3900. Phone: (210) 567-3939. Fax: (210) 567-6491. E-mail: baseman{at}uthscsa.edu

{triangledown} Published ahead of print on 14 April 2008.

Editor: A. Camilli

Infection and Immunity, July 2008, p. 3116-3123, Vol. 76, No. 7
0019-9567/08/$08.00+0     doi:10.1128/IAI.00173-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Balasubramanian, S., Kannan, T. R., Hart, P. J., Baseman, J. B. (2009). Amino Acid Changes in Elongation Factor Tu of Mycoplasma pneumoniae and Mycoplasma genitalium Influence Fibronectin Binding. Infect. Immun. 77: 3533-3541 [Abstract] [Full Text]  
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