Protein Interactions in the First Step of the Tetrapyrrole Pathway in Escherichia coli: GSAT and PBGS
Mentor:Luiza Nogaj, Dr. , Mount St. Mary's College
The tetrapyrrole pathway leads to the production of heme and chlorophylls. The intermediates produced in this pathway are toxic to the cell and the inactivation of porphobilinogen synthase causes porphyria, a light sensitivity disease. Due to the cause of this disease, we hypothesized that all the intermediates in this pathway are channeled without being released into the cellular environment. It was also hypothesized that the proteins in this pathway interact with each other and form protein complexes in order to channel the substrates. To test our hypotheses we cloned, overexpressed, and purified glutamate semialdehyde aminotransferase (GSAT) and porphobilinogen synthase (PBGS), one of the first enzymes in the tetrapyrrole pathway. Activity assays ran on PBGS indicated that the enzymes’ activity was increased with the addition of Mg2+ by ~79%. It was discovered that GSAT and PBGS interact with one another and this interaction is dependent on the GSAT cofactors. Further research will need to be done to examine substrate channeling between GSAT and PBGS.