The survival technique, carbon catabolite repression (CCR), is one of the most fundamental and oldest mechanisms used for environmental sensing and signalling in bacteria, and it's critical for successful competition in diverse and frequently changing conditions.
As a neutral molecule, glucose is able to pass freely in and out of a bacterium cell's membrane. When glucose is available as the energy source, the cell traps the molecule inside its walls by adding a phosphate called "phosphorylation" with the help of a phospho-relay system that requires a protein known as HPr.
HPr can itself be phosphorylated in two ways, with one form binding the CCR master regulatory protein, CcpA, and allowing them to then bind a large number of specific DNA sites on the bacterial chromosome. Such binding, in turn, redirects the metabolic program of the cell so only proteins that are needed for glucose metabolism are made.
When glucose is not present, HPr is not phosphorylated properly for CcpA binding, leading to CcpA falling off the DNA. This allows the cell to make other proteins that can break down alternative carbohydrates that are present in the environment.
"If you don't have any glucose, it's time to upregulate genes involved in the catabolism of secondary carbon sources," Brennan said.
Brennan said developing a visualization of a protein's structure through X-ray crystallography helps all biomedical scientists to better understand its function.
"Our major focus is to determine structures of proteins and their biologically relevant complexes so we can understand the biology more completely," he said. "My lab focuses on bacterial systems. If you can understand
Contact: Jonathan Modie
Oregon Health & Science University