Asp3 mediates multiple protein–protein interactions within the accessory Sec system of Streptococcus gordonii
Article first published online: 2 SEP 2010
Published 2010. This article is a US Government work and is in the public domain in the USA
Volume 78, Issue 2, pages 490–505, October 2010
How to Cite
Seepersaud, R., Bensing, B. A., Yen, Y. T. and Sullam, P. M. (2010), Asp3 mediates multiple protein–protein interactions within the accessory Sec system of Streptococcus gordonii. Molecular Microbiology, 78: 490–505. doi: 10.1111/j.1365-2958.2010.07346.x
- Issue published online: 12 OCT 2010
- Article first published online: 2 SEP 2010
- Accepted manuscript online: 24 AUG 2010 12:00AM EST
- Accepted 8 August, 2010.
Bacterial binding to human platelets is an important step in the pathogenesis of infective endocarditis. Streptococcus gordonii can mediate its platelet attachment through a cell wall glycoprotein termed GspB (‘gordonii surface protein B’). GspB export is mediated by a seven-component accessory Sec system, containing two homologues of the general secretory pathway (SecA2 and SecY2) and five accessory Sec proteins (Asps1–5). Here we show that the Asps are required for optimal export of GspB independent of the glycosylation process. Furthermore, yeast two-hybrid screening of the accessory Sec system revealed interactions occurring between Asp3 and the other components of the system. Asp3 was shown to bind SecA2, Asp1, Asp2 and itself. Mutagenesis of Asp3 identified N- and C-terminal regions that are essential for GspB transport, and conserved residues within the C-terminal domain mediated Asp3 binding to other accessory Sec components. The loss of binding by Asp3 also resulted in an impaired ability of S. gordonii to secrete GspB. These studies indicate that Asp3 is a central element mediating multiple interactions among accessory Sec components that are essential for GspB transport to the cell surface.