UH research discovers way to display disulphide-bonded proteins

Doctoral candidates at the UH Cullen College of Engineering have found a platform that may be useful for protein engineering by manipulating the surface proteins on bacterial cells. It was previously unknown if certain proteins — those containing disulphide bonds — could be moved from the inside of the cell to the surface of the cell and still support their functionality, said engineering doctoral candidate Balakrishnan Ramesh. It turns out that they can.

“People were not sure if proteins of interest, when they contain disulphide bonds, could be displayed on the surface (of cells) or not. We showed that it could be and that it is functional,” Ramesh said.

Moving proteins to the surface of cells is not a new application, said Navin Varadarajan, assistant professor at the College of Engineering. It was unknown if these disulphide-bond-containing proteins in particular could keep up their functionality after being moved on to the cell surface. Some of these proteins could be useful in protein engineering or degradation, he said.

“What we are trying to do now is a real application of this. Because we can study this one cell at a time, we can modify the property of any protein that’s being displayed on the surface,”Varadarajan said. “We can engineer the properties of whatever protein we’re interested in. We consider this a platform technology for engineering proteins of interest.”

The proteins that Varadarajan and Ramesh are interested in utilizing are inaccessible unless displayed on the surface of the cell. Diffusion into and out of a cell is considered a major problem, Varadarajan said.

“If you consider the proteins within the bacteria, they have no access to the outside. They’re stuck inside one or more lipid bi-layers. This makes it so that there is access to whatever you want,” Varadarajan said.

“Whatever you add into the solution containing the bacteria, the bacteria will have access to. I can bind to stuff; I can catalyze the reactions and do all kinds of stuff without having to worry about the molecule of interest having to diffuse into the cell.”

This new discovery could be useful in various applications from catalysis to vaccination, Ramesh said.

“We want proteins of interest on the surface of bacteria. These proteins of interest refer to proteins that are already useful for various applications,” Ramesh said.

“We could display enzymes on the surface and use it as a whole-cell catalyst for many reactions.”

Within their department, Varadarajan and Ramesh worked with associate professor Patrick Cirino to assist them by the sharing of equipment.

“His collaboration was extremely important in that sense,” Varadarajan said.

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