Did you know that the venom of a carnivorous sea snail can send an unsuspecting fish into a sugar coma? That's weird for a start, right? But get this: snail venom might also be behind the next generation of ultra-fast-acting insulin for diabetics.
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Biologists from the University of Utah discovered the insulin in the cone snail's venom last year. But it's taken until now for a team of Australian researchers to join their Utah counterparts and establish the insulin's three-dimensional structure and, most importantly, how it works.
It's a significant step that will enable scientists to set about making an artificial version of the snail's fast-acting insulin, for use in humans.
Currently it takes up to 15 minutes for regular insulin to take effect in diabetes patients, which number around 1.7 million Australians.
Walter and Eliza Hall Institute structural biologist Mike Lawrence said using the insulin found in the cone snail's venom as a model, it could become almost instantaneous in next generation insulins used by patients with type 1, type 2 and gestational diabetes.
"Our breakthrough has been to determine the structure of this venom insulin," he said. "The 'ah-ha moment' was realising that it doesn't have the hinge mechanism that human insulin does and then working out how it gets by without it."
Associate Professor Lawrence said while the insulin was made by a sea snail, it was designed to work on fish: a vertebrate species like humans. This is why he expects that the snail's venom insulin will prove effective in humans.
"Fish are closer to us than snails," he said.
The cone snail releases its unusual venom into the water for a passing fish to ingest through its gills, putting it into hypoglycaemic shock. That's when the murderous mollusc strikes and slurps up its prey.
"The fish is fast-moving and the snail is not fast-moving," he said. "So a snail needs to have a venom that is fast acting."
In humans, insulin is a protein made up of about eight amino acids that form a hinge. Without them, the hinge mechanism doesn't work and the insulin can't bind to the receptor on the surface of the cells.
The structure of the snail venom insulin is novel: it has a smaller substitute for the hinge made up of just one amino acid.
"It is unique to insulins, we've never seen this in insulins before," Associate Professor Lawrence said.
The study was an international collaboration involving American and Danish researchers as well as scientists from Australian institutions including the Walter and Eliza Hall Institute, Monash University, La Trobe University and Flinders University. The findings are outlined in the journal Nature Structural and Molecular Biology on Tuesday.
According to Diabetes Australia about 280 Australians develop diabetes every day - or one person every five minutes.
