Scientists develop new method for detecting functional sites on proteins

August 19, 2015

"But a small fraction of the cysteines showed a constant level of labeling for low and high concentration probes," said Wang, "indicating that they were hyper-reactive."

At first by examining select proteins from this group, and later by looking up all 522 labeled proteins in a database, the team found that the cysteines marked as hyper-reactive by their technique were highly enriched in known functional sites. The non-hyper-reactive cysteines, by contrast, were much less commonly listed as functional.

"By extrapolation, we can say that cysteines that haven't yet been officially characterized, but which show this hyper-reactivity in our assay, are likely to be functional," said Cravatt. To lend further support to this hypothesis, the team performed experiments, in collaboration with Scripps Research Assistant Professor Kerri Mowen, Ph.D, on an uncharacterized hyper-reactive cysteine in this list and showed that it played an important functional role in its parent proteins.

In a final set of experiments, collaborating investigator David Baker and colleagues at the University of Washington supplied a set of synthetic proteins that had been designed to work as enzymes. Weerapana and Wang and their team were able to predict, using their reactive-cysteine tagging technique, which of these proteins had the hoped-for enzymatic function.

"This is a relatively precise and straightforward method for screening designed proteins for functional properties," said Cravatt. "It could be very useful for creating new enzyme catalysts for basic research and industrial applications."

And cysteine is only one type of amino acid to which this basic technique could be applied. "All you would have to do, in principle, is change the reactive group on the probe, and instead of targeting cysteines, target lysines or serines or tyrosines, or some other amino acid," Cravatt said. "I think the approach will have broad utility in many areas of biology."

Source: The Scripps Research Institute