Dinosaur Bones

What ancient proteins can tell us about dinosaurs

by Dr. Barry Starr, Stanford University

Remember in Jurassic Park when they got dinosaur DNA from an ancient mosquito's stomach? Well, if they had been interested in dinosaur proteins, they only had to look at a dinosaur bone.

Dinosaur bones are at least 65 million years old. And all of the meat has turned to stone. Over this amount of time and with this much abuse, scientists thought no DNA or proteins could survive. They were wrong.

About a year ago, scientists were able to pull proteins out of a T. rex bone. Now they have done some additional work that suggests dinosaurs are closely related to birds. It is amazing that our technology has become so sensitive that we can examine dinosaur proteins.

The dinosaur came before the chicken or the chicken egg

Did birds come from dinosaurs?

For quite awhile now scientists have thought that birds may have evolved from dinosaurs. This new work provides some direct evidence that may strengthen this hypothesis into a theory.

One of the major proteins found in our bones is called collagen. Collagen is special in a lot of ways.

First there is a lot of it in a bone. If any amount of protein were to survive, it would be collagen.

Second, it is different than a lot of other proteins. It has special things done to it by the cell that make it very stable. These chemical modifications make it easy to distinguish from other proteins.

Finally, it has stayed very similar over time. This means there are changes we can find. But not so many that we can't tell what we have.

So some scientists did some experiments on a particularly well-preserved T. rex thigh bone. First they demineralized it. Basically they added something (EDTA) to help turn the stone back into bone.

Then they checked what was there with antibodies. Antibodies can tell whether or not a certain protein is there. They can be very specific—some recognize just one part of a protein from one type of plant or animal.

When scientists added antibodies that recognized chicken collagen to the demineralized bone, the antibodies stuck. This told them that there was collagen there. And that it was similar enough to the chicken protein to be recognized.

OK but how much like a chicken is it? To figure this out, the scientists decided to look right at the protein. They used a technique called mass spectrometry (mass spec).

In mass spec, a protein is chewed up in a specific way and the pieces identified. Scientists can then compare the chewed up protein to known proteins and see how related they are.

When they did this, they found that the T. rex collagen was most similar to chicken collagen. Next were newts and frogs. Others were much less related.

So chickens came from dinosaurs, right? Well, maybe.

Unfortunately, the scientists didn't have alligator or crocodile collagen to compare it to. Once we see how related these beasts are to a T. rex, we'll have a better feel for how related a chicken and a dinosaur are.

One thing is for sure, a chicken and a dinosaur are very related. And now that we have this technique, I am sure lots of other collagens will be figured out. Then we'll be able to tell whether the dinosaur came before the chicken. Or its egg.

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From protein to DNA

We can go from protein to DNA.

So a dinosaur has a collagen protein that is very similar to a chicken's. What does this actually mean? And can we clone a dinosaur with this knowledge?

Proteins are made up of around 20 different amino acids. All the complexity we see around us comes from different arrangements of these 20 molecules.

Which proteins are made when and where is decided by our genes. Genes really are just recipes for proteins. The recipe is just instructions for putting together a string of amino acids in a certain order.

What the researchers got out of their experiments were strings of amino acids. For example, they got the following from the T. rex:

GVQGPPGPQGPR

Each letter is a different amino acid. For example, G is glycine and P is proline.

They then looked at other creatures to see what string of amino acids they have. The chicken, for example, has:

GVQGPPGPQGPR

As you can see, this is an exact match. The newt on the other hand, had:

GAAGPPGATGFP

This is pretty different for this piece of the protein. When they did this with many pieces of the protein, they came up with a number of 58% sequence identity (the same amino acids in the same order) for the chicken. And 51% for the frog and newt.

So can we clone a dinosaur from information like this? Probably not.

We can certainly go backwards from amino acid to gene. In other words, if we know the amino acids of a protein, we can create a gene to make it.

Because there are multiple ways to make some of the amino acids, the gene may not be exactly right. But we can make a gene that has the recipe for the protein.

Of course this is just one protein. Out of tens or hundreds of thousands. We would need to repeat this for most if not all of the dinosaur's proteins.

And many proteins are not found in the adult. Which means we might need to look at many, many different stages of development to get the genes right.

Even if we did all of this, we still wouldn't be able to do it. This is because there is more to a gene than the protein recipe. There are also instructions for when and where to make the protein. These instructions are not available from protein data.

When an organism develops, genes are turned on and off in a precise pattern. They are on in some cells, and off in others. They may be on in day 4 of development but not day 8.

This information is contained in the DNA too. But is not found in the protein itself.

So this is not a route to cloning a dinosaur. Frankly, even if we find some dinosaur DNA, we probably won't be able to clone a dinosaur anytime soon. See below for the details.

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Content provided by the Department of Genetics, Stanford University.