Corynebacterium glutamicum possesses two secA homologous genes that are essential for viability
- PDF / 329,994 Bytes
- 6 Pages / 595 x 791 pts Page_size
- 75 Downloads / 188 Views
S H O R T CO M MU N I C A T I O N
Corynebacterium glutamicum possesses two secA homologous genes that are essential for viability Michael Caspers · Roland Freudl
Received: 26 July 2007 / Revised: 17 December 2007 / Accepted: 15 January 2008 / Published online: 2 February 2008 © Springer-Verlag 2008
Abstract SecA is a central component of the bacterial Sec preprotein translocase. Besides the housekeeping SecA (SecA1), some mostly pathogenic Gram-positive bacteria possess an accessory SecA (SecA2) that is involved in the export of a few substrates only. Here we show that neither of the two secA homologous genes present in the genome of the non-pathogenic bacterium Corynebacterium glutamicum can be deleted, unless a copy of the respective gene is provided in trans on a plasmid. This Wnding is in marked contrast to all other cases examined so far making C. glutamicum the Wrst reported bacterium possessing two essential SecA proteins. Keywords Gram-positive bacteria · Corynebacterianeae · Protein secretion · Translocase subunit · SecA
Introduction All living organisms need to transport proteins across hydrophobic membranes to their site of action. In eubacteria, the majority of extracytosolic proteins is translocated across the plasma membrane via the general secretion (Sec) pathway, that has been extensively studied in Escherichia coli, Bacillus subtilis and other bacteria (for reviews see van Wely et al. 2001; de Keyzer et al. 2003). Secretory proteins are initially synthesized as larger preproteins containing an N-terminal signal peptide that is cleaved oV by signal peptidase
Communicated by Arnold Driessen. M. Caspers · R. Freudl (&) Institut für Biotechnologie 1, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany e-mail: [email protected]
during or shortly after translocation (von Heijne 1998). The actual movement of preproteins across the cytoplasmic membrane is catalyzed by a multimeric membrane protein complex called preprotein translocase. The core of the translocase consists of a proteinaceous channel formed by the heterotrimeric membrane protein complex SecYEG (Osborne et al. 2005) and the peripheral ATPase SecA as molecular motor (Vrontou and Economou 2004). Consecutive cycles of ATP-binding and hydrolysis by SecA are thought to facilitate the stepwise transport of preproteins (Mitra et al. 2006). In addition, translocation is stimulated also by the proton motive force once the translocation reaction has been inititated by SecA and ATP (Schiebel et al. 1991). Besides the classical Sec components, certain mostly pathogenic Gram-positive bacteria have recently been found to possess an additional SecA and, in some cases, also an additional SecY protein, termed SecA2 and SecY2, respectively (Braunstein et al. 2001; Bensing and Sullam 2002; Lenz and Portnoy 2002; Chen et al. 2004). Whereas the classical SecA and SecY proteins (termed SecA1 and SecY1) are indispensable for viability and are responsible for exporting the vast majority of all extracytosolic proteins, the Sec2 components were found to be i
Data Loading...
