Proteomic analysis of the peroxisomal membrane of Penicillium chrysogenum
|PhD ceremony:||Ms M. Woszczynska|
|When:||October 10, 2014|
|Supervisor:||prof. dr. A.J.M. (Arnold J M) Driessen|
|Where:||Academy building RUG|
|Faculty:||Science and Engineering|
Penicillium chrysogenum is a filamentous fungus used in the production of penicillin antibiotics at an industrial scale. Penicillins have a common structure but the various antibiotics have different side chains. During biosynthesis the core structure is build in the cytosol of the fungus whereas the side chain is attached in subcellular compartment termed microbodies. Side chains are usually organic acids that first need to be activated with coenzyme A. This reaction requires energy in the form of ATP. However, the ATP is produced in the cytosol and first needs to enter the microbody before side chain activation can occur. In this work we have identified a microbody localized transporter responsible for the uptake of ATP into the microbody. Gene inactivation of this transporter severely inhibits penicillin production.
Industrial Penicillium strains are the result of a lengthy classical strain improvement programme where the fungus was subjected to chemical agents that caused genome wide mutations as well as multiplication of the genes responsible for penicillin biosynthesis. This gene cluster contains three genes and in an earlier production strain they are present in 8 copies. To determine the gene dosis effect, we used a high yielding P. chrysogenum strain in which the copy number was varied between 1 and 8. Penicillin production did not increase linearly with the gene copy number but started to saturate already at a gene copy number of 2 to 3. Further analysis revealed that the saturation is due to a nonlinear increase of the microbody localized acyltransferase that attaches the side chain in the microbody to the penicillin core structure. Our results demonstrate that microbodies play a key role in penicillin production and provide new leads to improve on the production of this important class of antibiotics.