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OnderzoekGBBMolecular MicrobiologyResearch

Research

The objective of the research in our group is to elucidate the molecular mechanisms of bacterial protein export and solute transport. The solute transport systems are studied in bacteria, archaea and lower eukaryotes. The emphasis of the work is on the energetics and kinetics of the translocation processes, and the structure analysis of the proteins; the role of transport processes in the physiology of the micro-organisms is also studied. Our different subjects are:

  • Protein translocation and membrane protein assembly
  • Extremophiles
  • Multidrug resistance
  • Transport processes in Penicillium chrysogenum
  • Structure and function of secondary transporters
  • Bacterial Cell division

Below you can find a short description about the research in the different research units. For more detailed information either follow the link in the left menu or contact the person noted in the short descriptions.

Protein translocation and membrane protein assembly

In cells of all kingdoms of life (eukaryotes, prokaryotes and archaea) proteins are targeted to membranes after which they are inserted into or translocated across the membrane to fulfill their functions. These processes are essential for the viability of the cell. Several mechanisms for secretion and membrane insertion of proteins have been found.
The Sec (which stands for secretion) system is considered to be the most important pathway as most proteins use this system and it is present in all organisms studied sofar. We study the bacterial Sec pathway in Escherichia coli and in Bacillus subtilis .

For more information contact Prof. A.J.M. Driessen.

Extremophiles

We are interested in the study of transport processes across archaeal membranes. Archaea are known to inhabit very hostile environments. Our model organisms are Sulfolobus solfataricus, prefers growth conditions of 80oC and pH3. The characterized sugar uptake systems of this archaeon showed interesting adaptations to the extreme environment in which it thrives. The extracellular components of the Sulfolobus solfataricus transporters contain bacterial type IV pilin like signal peptides. Recently, we identified and characterized the archaeal type IV pilin peptidase. Current research is focussing on the type IV pilin like-secretion system in Sulfolobus solfataricus.

For more information contact Prof. A.J.M. Driessen.

Multidrug resistance

Cells can acquire multidrug resistance (MDR) against a variety of unrelated drugs by the expression of membrane embedded multidrug transport proteins that are able to expel these drugs from the cell before they can reach their target. As a consequence, MDR is a major problem in the treatment of infectious diseases and of cancer. In cancer cells, several MDR transporters have been identified, of which P-glycoprotein and MDR-associated protein, MRP1, are the best known. In the Gram-positive bacterium L. lactis, an organism used in food manufacturing, resistance to toxic hydrophobic cations is mediated by two distinct MDR transport proteins: LmrP, belonging to the major facilitator superfamily, and the ATP-binding cassette transporter LmrA. Our major goal is to elucidate the mechanism of drug inding, and how energy transfer is coupled to drug translocation.

For more information contact Prof. A.J.M. Driessen.

Transport processes in Penicillium chrysogenum

The penicillin biosynthesis pathway in Penicillium chrysogenum starts in the cytosol with the condensation of a-aminoadipate, cysteine and valine to form the tripeptide ACV. The intracellular concentration of a-aminoadipate has been shown to be limiting for the formation of ACV and the overall synthesis rate of penicillin. Addition of exogenous a-aminoadipate increased the internal a-aminoadipate pool thereby stimulating penicillin biosynthesis. This indicated the presence of an uptake system that is possibly involved in the retention of the intracellular a-aminoadipate pool. Studies on the mechanism of a-aminoadipate uptake by P. chrysogenum indicated that it is the substrate of a dicarboxylic amino acid permease. Using a set of degenerated PCR primers, the gene of an amino acid transporter of P. chrysogenum has been isolated, that showed high homology with the dicarboxylic amino acid transporter Dip5 of Saccharomyces cerevisiae. The gene was expressed in an S. cerevisiae strain deficient in uptake of acidic amino acids, and overexpressed in E. coli for protein purification and reconstitution in vesicles. These studies will reveal the substrate specificity of the transporter.

For more information contact Prof. A.J.M. Driessen.

Structure and function of secondary transporters

Secondary transporters are the simplest ones among biological systems that transport solutes across biological membranes. All they do, and some not even this, is to couple the translocation of a substrate to the translocation of one or more co-ions. This allows them to accumulate the substrate inside the cell. Maybe because of their simplicity, secondary transporters are very abundant in nature and found in all types of biological membranes, from prokaryotes to higher organisms. 
The project focuses on three aspects related to secondary transporters, (i) biochemical approaches to structure/function relationships of secondary transporter proteins, (ii) the function of the transporters in the physiology of the organism, (iii) bioinformatics & membrane proteins.

For more information contact Dr. Juke Lolkema.

Bacterial cell division

We study fundamental aspects of division in two well characterized model bacteria. Cell division appears simple, with a bacterium growing, splitting through the middle after which the two bacteria start growing again. This division process involves the coordinated action of a large number of proteins that ensure that division occurs at exactly the right time and place, the middle of the cell. Cell division starts with the formation of a ring composed of protein filaments of FtsZ, just underneath the membrane. This ring organizes all other proteins that play a role in division. Together, these proteins are proposed to form a large multi-protein machinery, called the divisome.

Our work addresses three fundamental questions about bacterial division. The goal of our work is to generate important novel insights in how bacteria regulate their replication.

For more information contact Dr. Dirk-Jan Scheffers

Last modified:26 February 2013 4.18 p.m.