The twin-arginine translocation network of Bacillus subtilis

PhD ceremony: Mr. C.G. Monteferrante, 12.45 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: The twin-arginine translocation network of Bacillus subtilis

Promotor(s): prof. J.M. van Dijl

Faculty: Medical Sciences

The transport of proteins across biological membranes is crucially important for all living organisms, since the transported proteins are involved in many vital processes. Consequently, protein transport processes need to be tightly regulated so that the proteins reach their correct destination and are used in the right cellular process. This aspect is also of great importance in bacterial cells since numerous vital processes rely on proper localization of proteins to specific sub-cellular compartments or the extracellular environment. For this reason, several different protein transport machineries have evolved. The Gram-positive soil bacterium Bacillus subtilis is one of the microorganisms that is frequently used for fundamental research on protein transport, as well as the biotechnological production of secreted enzymes. Notably, this microorganism possesses different secretion pathways that are used to move proteins to different destinations within and outside the cell. One of these, the so-called twin-arginine translocation (Tat) system, recognizes proteins with a twin-arginine motif in their signal peptide and secretes them in a fully folded state. The results presented in this thesis provide completely new insights into the global network organization, three-dimensional structure, and quality control mechanisms that are relevant for transporting proteins via the Tat system to the membrane, cell wall or growth medium of B. subtilis . In addition, environmental conditions are shown to have significant impact on the fidelity of protein transport via the Tat system. Together, these findings provide new insights into the working mechanism, and leads to future applications of the Tat system in B. subtilis .