In this study, researchers estimated a new drug for analyzing function of proteins in disease and health. Antibodies made by camels, llamas and alpacas allow scientists to study the structure and function of proteins in disease and health. While valuable, the approach is time-consuming, costly and often unsuccessful. This study is published in the journal of Nature Structural and Molecular Biology.

It is a little-known fact that llamas, alpacas, camels and other members of the camelid family make a unique class of antibodies that allow scientists to determine the structures of otherwise impossible-to-study proteins in the body, understand how those proteins malfunction in disease and design new drugs that act on them.

Lock and key

The active segments of camelid antibodies are often called nanobodies because they can be much smaller than regular antibodies. A llama nanobody might bind only to a conformation for example, "open" or "closed" of a protein. Nanobodies also can bind to challenging proteins, such as receptors that work in oily cell membranes.

Structural biologists like Kruse and Manglik want to find the exact nanobody that matches their protein of interest so they can lock the protein in one position and run tests to figure out its atomic structure. Learning the structure allows them to study how the protein works and provides a blueprint for designing drugs that target it.

Nanobodies have opened long-locked doors in biomedical science. For example, they have allowed researchers to see for the first time how neurotransmitters such as adrenaline and opioids bind to receptors in the brain. Each yeast cell has a slightly different nanobody tethered to its surface, made by a slightly different piece of synthetic DNA.

The researchers mixed all the yeasts together and froze them for safekeeping. Anytime they want to run an experiment, they simply defrost a test tube's worth: a miniature llama immune system.

Researchers developed a method where, instead of injecting a llama, scientists can now label their protein of interest with a fluorescent molecule and add it to the test tube.

Yeast with surface nanobodies that recognize the protein will glow. The researchers then use fluorescence-activated cell sorting, or FACS, to separate the glowing yeast from the rest. They sequence the DNA of those glowing yeast cells to learn what the nanobodies are. They can then use E. coli bacteria to grow as many of those nanobodies as they need.

"Nanobodies are making it possible to develop drugs for biological targets that antibodies were simply too big to hit," said Manglik. "By making nanobody discovery quick and easy, we hope our platform will dramatically accelerate the potential applications of this exciting technology."