IAI Accepts, published online ahead of print on 26 October 2009

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Infect. Immun. doi:10.1128/IAI.00958-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

The Stability of Cytadherence Proteins in Mycoplasma pneumoniae Requires Activity of the Protein Kinase PrkC

Sebastian R. Schmidl, Katrin Gronau, Claudine Hames, Julia Busse, Dörte Becher, Michael Hecker, and Jörg Stülke^*

Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University Göttingen, Germany; and Institut für Mikrobiologie und Molekularbiologie, Ernst-Moritz-Arndt-Universität Greifswald, Germany

^* To whom correspondence should be addressed. Email: jstuelk{at}gwdg.de.

Mycoplasma pneumoniae belongs to the mollicutes, a group of bacteria with strongly reduced genomes, that are nevertheless capable of independent life. With only three transcription factors, the regulatory features of these bacteria are very limited. Thus, posttranslational regulation might be important for M. pneumoniae. In addition to the highly specific HPr kinase, the M. pneumoniae prkC gene encodes the serine/threonine protein kinase C. In order to study the function(s) of this kinase, we isolated a M. pneumoniae mutant affected in PrkC. This mutation resulted in non-adherent growth and loss of cytotoxicity. Examination of the phosphorylation profile of the prkC mutant suggested that phosphorylation of cytadherence proteins was affected by the loss of this kinase. In contrast, inactivation of the prpC gene affecting the protein phosphatase that antagonizes PrkC-dependent phosphorylation resulted in more intensive phosphorylation of the cytadherence proteins HMW1, HMW3, of the major adhesin P1 and of the surface protein MPN474. Moreover, loss of PrkC does not only affect the phosphorylation state of the cytadherence proteins but also their intracellular accumulation. However, the expression of the corresponding genes was not affected by PrkC suggesting that PrkC-dependent phosphorylation results in stabilization of the cytadherence proteins. The HMW proteins and P1 are part of the so-called terminal organelle of M. pneumoniae that is involved in gliding motility, cell division and adhesion to host epithelial tissues. Our observations suggest that the post-translational modification of cytadherence proteins by PrkC is essential for the development and function of the M. pneumoniae terminal organelle.