Menlo Park, Calif.Calcium regulates many critical processes within the body, including muscle contraction, the heartbeat, and the release of hormones. But too much calcium can be a bad thing. In excess, it can lead to a host of diseases, such as severe muscle weakness, a fatal reaction to anesthesia or sudden cardiac death.
Now, using intense X-rays from the Stanford Synchrotron Radiation Lightsource (SSRL) at the Department of Energy's SLAC National Accelerator Laboratory, researchers have determined the detailed structure of a key part of the ryanodine receptor, a protein associated with calcium-related disease. Their results, which combine data from SSRL and the Canadian Light Source, pinpoint the locations of more than 50 mutations that cluster in disease "hotspots" along the receptor.
"Until now, no one could tell where these disease mutations were located or what they were doing," said principal investigator Filip Van Petegem of the University of British Columbia in Vancouver.
The ryanodine receptor controls the release of calcium ions from a storehouse within skeletal-muscle and heart-muscle cells as needed to perform critical functions. Previous studies at lower resolution indicated that mutations cluster in three regions along the receptor, but without more detailed information it remained unclear exactly how they contributed to disease.
In a study published this week in Nature, Van Petegem and his group describe the structure of one of these hotspots in extremely fine detail and predict how the mutations might cause the receptor to malfunction and release calcium too soon.
The receptor is made up of more than 20,000 molecules called amino acids. Van Petegem's group studied a string of about 560 amino acids, where they found 57 mutations. In 56 cases, the mutations involved a change in a single amino acid, while the last one involved a deletion of 35 amino acids from the string.
|Contact: Melinda Lee|
DOE/SLAC National Accelerator Laboratory