蛋白质活动控制新发现 | 蓝月 | News
Published online: 16 December 2004; | doi:10.1038/news041129-11
Proteins come under new control
Helen Pearson
Fundamental manager of cell activity proposed.
In a finding that could change thinking about the cell's fundamental machinery, US scientists have discovered a brand new way that proteins may be galvanized into action.
Of the tens of thousands of proteins working within a cell, the vast majority are activated or disabled by the addition of a chemical group called a phosphate. This process is vital to control proteins, which together drive everything in our bodies from growth to movement to thought.
Biologists have long assumed that phosphate groups are added almost exclusively by a single, well-understood method. A protein steals the phosphate from a molecule called adenosine triphosphate (ATP), with the help of an enzyme called a protein kinase.
Now Solomon Snyder at Johns Hopkins University in Baltimore, Maryland, and his colleagues are challenging that view. In a paper in Science, they reveal an entirely new way in which phosphates are added to proteins, and hence cells' actions may be controlled.
If it holds up, "it would be a spectacular finding," says biochemist John York of Duke University Medical Center in Durham, North Carolina. It implies that perhaps tens or thousands of proteins are being controlled by a previously unrecognized means.
"It's a pretty fundamental change in our view of how things are going on in the cell," adds Robin Irvine, who studies intracellular signalling at the University of Cambridge, UK.
Second cycle
The discovery in the 1940s and 50s that adding a phosphate group can change a protein's activity is considered fundamental in cell biology: it won its discoverers, Edmond Fischer and Edwin Krebs, a Nobel prize in 1992. The process allows cells to sense things on the outside, and change what they are doing on the inside.
For example: after a meal, proteins in the outer coat of a cell detect the hormone insulin; this activates a protein kinase, which transfers phosphate groups from ATP to a series of other proteins; together, this army of proteins prompt the cell to start taking up sugar circulating in the blood.
Instead of ATP, Snyder and his team propose that a molecule called IP7 transfers one of its seven phosphate groups to another protein, without the help of an enzyme.
To demonstrate this, they radioactively tagged one of the phosphates on IP7, before mixing it with a slurry of proteins extracted from yeast, mice or flies. They showed that the radioactive phosphate wound up attached to a plethora of other proteins, and went on to identify a handful of them.
Snyder speculates that interfering with IP7 might, one day, be used to treat certain diseases. If, for example, IP7 normally fires up a protein that triggers cancer, then blocking that activation could help fight the disease.
York counters that this is "a huge stretch". He and others in the field say they would like to see much more evidence before they are convinced that IP7 is as crucial in cell biology as ATP.
For example, scientists need to prove that IP7 adds phosphates to many more proteins than those demonstrated, and that this actually alters what they do in the cell. The IP7 discovery is not yet as big a deal as the ATP find, says York, "but maybe it'll just take time to figure out."
来源:http://www.nature.com/news/2004/041213/full/041213-11.html2004-12-17 8:21:44 |
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