With many more laboratories becoming involved in crystallising proteins, the scientists are confident this new method will yield new information and go some way to eliminate the `bottleneck of crystallisation' that occurs when determining a three-dimensional protein structure.
Researchers from the Midwest Centre for Structural Genomics (MCSG), the Structural Genomics Consortium (SGC) and the Structural Biology Centre (SBC) at the U.S. Department of Energy's Argonne National Laboratory attempted to increase the efficiency of the crystallisation process by inserting a protease within the protein's structure.
The protease preferentially bound to the proteins at the regions of most disorder, cutting off the loose ends. The researchers then crystallised and examined nine of these newly shorn proteins that previously had resisted attempts to study them using X-ray crystallography.
This process, known as 'limited in situ proteolysis,' represents one of several potential 'salvage pathways' that biophysicists could use to create more usable protein crystals and reduce waste.
Currently, scientists' efforts to manufacture and then study a workable crystal on Argonne's Advanced Photon Source yield structural data only about 15 per cent of the time. By using proteases to digest part of the protein sample, the Argonne scientists achieved a six per cent boost in efficiency.
"This simple technique offers an opportunity to uncover and characterise the structures of dozens of proteins that up until now we had to study using much more laborious and expensive approaches," said Argonne senior biologist Andrzej Joachimiak, who led the Argonne research effort.
"We've tried to find a way to remove the disordered parts using computer modelling, but that's been a challenging process. This new experimental method is fast, inexpensive and can be applied to many different targets, from bacterial pathogens to human proteins," he added.
More and more significant proteins are being submitted to laboratories for crystallisation and traditionally certain criteria needs to be set before crystallisation trials are started, such as solubility, purity and aggregation tendencies.
Robots now place a major role in facilitating the screening of crystallisation conditions. In cases where no crystals have been obtained after initial screening it can now be decided which possible modifications can be made to the protein itself to improve the chances of obtaining crystals.
This new method id welcome news giving scientists another avenue in which to investigate exactly how a protein's structure affects its form and function. Crucially, the method is cheap and relatively efficient, giving it an important advantage to cash-strapped laboratories or research institutions.
However, Joachimiak warned that scientists do not have a way to successfully crystallise every protein, even with the use of proteolysis. "There will still be some that are resistant," he added, "but we are making strides in our understanding of how exactly these essential substances work."
The research paper: 'In situ proteolysis for protein crystallization and structure determination," appears in the Nature Methods research journal.
