Investigators at Argonne National Laboratory have determined the structure of a key protein domain in a bacterium Geobacter sulfurreducens, an organism known for its ability to fix some heavy metals. The research might have future implications for such things as developing methods to decontaminate polluted or radioactive land sites, or possibly, diagnostics.
The researchers, led by Argonne senior biophysicist Marianne Schiffer, characterized the structure of one of the principal domains in a protein responsible for certain types of movement exhibited by the bacterium Geobacter sulfurreducens.
Geobacter lives in predominantly low oxygen environments and generates energy by transferring electrons to various metallic electron-accepting atoms such as iron or uranium. This ability suggests that Geobacter might be used for remediation of certain types of hazardous waste. For example, when uranium is reduced by this process to its insoluble form, it no longer leaks into groundwater and engineers can inexpensively remove the precipitated uranium.
To get to regions of high nutrient concentration (or to escape from harmful substances), certain types of bacteria use a mechanism called chemotaxis. For chemotaxis to work reliably, the cell must be able to convert external chemical information into internal chemical processes – this process is known as signal transduction. “One of the big questions in biology is how signals get from outside the cell to inside the cell,” Schiffer said.
The researchers determined the three-dimensional structure of a sensory domain of a membrane-spanning protein which they believe is involved in signal transduction. Schiffer and her colleagues were particularly interested in this domain because it contains heme, a molecular component that is common in oxygen transport proteins, such as hemoglobin, or in other proteins involved in respiration or photosynthesis. While other sensor proteins that contain heme have also been described, this is the first example of a sensor protein that contains a heme covalently bound to the protein, Schiffer said.
Press release: Scientists characterize protein structure of environmentally friendly bacteria …
Image caption: Three dimensional structure of the sensory domain of the bacterium Geobacter sulfurreducens showing two identical protein domains interacting with each other as observed in the crystal structure. The two protein domains are represented as ribbons (light blue and purple) and the heme in each protein domain is shown as “stick” model (green and gray).