Scientists discover milk proteins from cockroach embryo

Scientists discover milk proteins from cockroach embryo

Bangalore (ISJ) - A team of Indian and international scientists have discovered milk proteins in the embryo of a species of cockroach. It all began with curiosity. When Nathan Coussens, a young researcher at Iowa University noticed shiny crystals spilling out of a roach?s gut, he was intrigued. He showed the crystals to a fellow researcher who dismissed them as organic salt crystals commonly found in the gut of insects, birds and reptiles. But Coussens thought they were special, and so they turned out to be. The crystals were made of milk protein.

It was while working on a roach species called Diploptera punctata at the University of Iowa, that Coussens first discovered these crystals. D. punctata is a strange insect with a mammal-like quality ? it ?lactates?, producing milk to feed its brood. The crystals that Coussens had found were actually milk proteins that had crystallised within the guts of roach younglings.

Now, nearly 10 years after the initial discovery of the crystallised milk proteins, their structure has been solved by an international team of scientists including those from the Institute for Stem Cell Biology and Regenerative Medicine (inStem), Bangalore.

?We were not looking for nutritional supplement.� Nathan Coussens when working in Prof. Barbara Stay?s lab, isolated these in vivo grown crystals and we examined them out of curiosity.� The fact that they turned out to be nutritional food was a discovery� that happened when we followed our curiosity,? Professor S. Ramaswamy, then a faculty member at the University of Iowa and now a faculty member at inStem told Indian Science Journal.

Although protein crystals obtained from living systems are not unknown, these are generally formed within cells, tending to be small and limited in size by the volume of the cell they grow in. Such crystals are not very useful for studies on protein structure. In contrast, the milk crystals within roach guts grow large enough to be used for X-ray crystallography, a technique employed to elucidate protein structure.

To begin with, not only are there proteins with three different amino acid sequences, the proteins are also decorated with sugars called glycans. Furthermore, these proteins also form barrel-like shapes within which they bind molecules of fat. The crystals are made up of a mixed bag of molecules.

Yet here was a protein mixture with hugely variable components that nonetheless gave beautiful crystals which diffracted amazingly well. Despite their motley nature, the milk protein crystals from D. punctata diffract at a resolution of 1.2 angstroms ? enough to determine the positions of individual atoms in proteins.

Armed with the gene sequences for these milk proteins, Ramaswamy and colleagues plan to use a yeast system to produce these crystals en masse. He said, the nutritional contents in cockroaches are equivalent or more compared to commonly available dairy milk ?based on calorific value calculations?.

But converting the crystals into nutritional supplement is a huge challenge, admitted Prof. Ramaswamy. ?Right now we think the only way to do this is to use modern biotechnology tools and produce these recombinantly.?

The immediate challenge to Prof. Ramaswamy and his team is to show that it is safe for human consumption. ?The road is still long,? he rued. ?What we have made is a discovery. We need to now develop this into a product and show that it is safe.?

Source: �With inputs from inStem


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