Chaperones for climate protection

Jan 14, 2010
Rubisco binds carbon dioxide and facilitates the conversion to sugar and oxygen. Image: Andreas Bracher / Max Planck Institute of Biochemistry

(PhysOrg.com) -- The World Climate Conference recently took place. Reports about carbon dioxide levels, rising temperatures and melting glaciers appear daily. Scientists from the Max Planck Institute (MPI) of Biochemistry and the Gene Center of Ludwig Maximilians University Munich have now succeeded in rebuilding the enzyme Rubisco, the key protein in carbon dioxide fixation.

"Rubisco is one of the most important proteins on the planet, yet despite this, it is also one of the most inefficient", says Manajit Hayer-Hartl, a group leader at the MPI of Biochemistry. The researchers are now working on modifying the artificially produced Rubisco so that it will convert more efficiently than the original . Their work has now been published in Nature (Nature, January 14, 2010).

Photosynthesis is one of the most important biological processes. Plants metabolize carbon dioxide and water into oxygen and sugar in the presence of light. Without this process, life on earth as we know it would not be possible. The key protein in , Rubisco, is thus one of the most important proteins in nature. It bonds with carbon dioxide and starts its conversion into sugar and oxygen. "But this process is really inefficient", explains Manajit Hayer-Hartl. "Rubisco not only reacts with carbon dioxide but also quite often with oxygen." This did not cause any problems with the protein developed three billion years ago. Back then, there was no oxygen present in the atmosphere. However, as more and more oxygen accumulated, Rubisco could not adjust to this change.

The protein Rubisco is a large complex consisting of 16 subunits. Up to now, its complex structure made it impossible to reconstruct Rubisco in the laboratory. To overcome this obstacle, scientists at the MPI of Biochemistry and at the Gene Center of the Ludwig Maximilians University Munich used the help of cellular chaperones. The French term chaperone describes a woman who accompanies a young lady to a date and takes care that the young gentleman will not approach her protégé improperly. The molecular chaperones within the cell work in a similar way: They ensure that only the correct parts of a newly synthesized protein will come together. As a result of this process, the protein acquires its correct three dimensional structure. "With 16 subunits like those of Rubisco, the risk is very high that the wrong parts of the protein clump together and form useless aggregates," says the biochemist. Only with its correct structure will Rubisco be able to fulfil its function in plants.

The MPI researchers showed that two different systems, called GroEL and RbcX, are necessary to produce a functional Rubisco complex. The next aim of the scientists is to genetically modify Rubisco so that it bonds with carbon dioxide more often and metabolizes oxygen less frequently. "Because the modified Rubisco is predicted to absorb carbon dioxide from the atmosphere more effectively," says Manajit Hayer-Hartl, "it would enhance crop yields and could also be interesting for climate protection."

Explore further: Researchers create designer 'barrel' proteins

More information: C. Liu, A. L. Young, A. Starling-Windhof, A. Bracher, S. Saschenbrecker, B. Vasudeva Rao, K. Vasudeva Rao, O. Berninghausen, T. Mielke, F. U. Hartl, R. Beckmann and M. Hayer-Hartl, Coupled chaperone action in folding and assembly of hexadecameric Rubisco. Nature, January 14, 2010

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User comments : 13

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Ronan
not rated yet Jan 14, 2010
Ooh, now this IS interesting. It'd be fantastic if humans could come up with a photosynthesis system more efficient than C4, C3, or CAM...I mean, I suppose such a thing could have bad effects (although, as far as I know space, water, and sunlight, and not [CO2], are generally the limiting factors for plant growth), but if we created a plant that could handle CO2 and reject oxygen more efficiently, that...wouldn't be a bad legacy for our species. I can imagine such plants prolonging life on Earth for a few hundred million years if CO2 levels drop below what C4 and CAM plants can normally happen, in the far-distant future. Again, not a bad legacy.
Sean_W
not rated yet Jan 14, 2010
I have nothing against CO2 in the air but making crops more efficient will reduce land use and reduce the costs of foods and any product made with vegetable matter. Cotton would use less water if it could grow faster. Alter bamboo hemp and other non-food crops and it might reduce the need for forest products for paper and wood (a wood substitute can be made from some form of pressure treated bamboo I seem to recall). Is it safe to assume that algae use this enzyme as well?
PinkElephant
1 / 5 (1) Jan 14, 2010
Now here's a funny thing. What if this new and improved gene leaks out into the wild, and spreads all across the biosphere... permanently altering the natural balance (such as it is) between carbon fixation and outgassing... thereby, over millions of years, scrubbing too much CO2 from the atmosphere... thereby, throwing the planet back into a snowball state, killing off most of the plants, and consequently pretty much all the animals... Oopsie

On the other hand, it takes some hubris to think one could genetically tweak such a key element, that hasn't already been optimized over hundreds of millions of years. There may very well be good reasons why this protein is so "inefficient" -- it could well be that by tweaking it, you subject the plant to a deadly disease or two, or perhaps you so disrupt the cells' chemistry, that the plant commits suicide...

Well, either way, good luck.
Parsec
3 / 5 (1) Jan 14, 2010
While I agree with PinkElephant that it is unlikely that we could optimize this protein better and also incorporate it into actual plants, I suspect that the reason that it also reacts with Oxygen is that too high of an cellular oxygen level is bad for plants, and this protein has a secondary scavenger role that reduces oxygen free radical accumulation. Thats just a guess...

However, I do find it quite likely that scientists will be able to optimize the protein for use in non-biological CO2 scrubbers that convert CO2 to organic products using sunlight. This would be quite cool, photocells that directly produce bio-fuel instead of electricity.
JayK
1 / 5 (2) Jan 14, 2010
Evolution doesn't result in optimization for environments, so I'm not sure why PinkElephant and Parsec, two normally very intelligent people, have implied, or outright said as much. Evolution only selects for organisms that are best adapted to changing environments, but the best adapted doesn't mean the optimal. Saying that evolution creates an optimal gives the impression that there are goals that evolution is targeted towards, which is incorrect.
PinkElephant
not rated yet Jan 15, 2010
@JayK,

Let's say plant X gets a mutation, that endows it with a far more efficient carbon-fixation protein relative to all other plants. Would you, JayK, say that plant X suddenly has a huge advantage, and therefore will be favored by natural selection?

This is quite independent of any environment: if you can fix carbon more efficiently, you can photosynthesize, grow, reproduce, and survive better.

So when it comes to such a KEY part of photosynthesis, which is such a KEY factor in plant survival and overall well-being, then yes indeed I would expect pretty much all the biochemical components of this process to have become highly optimized over the last 3-4 Billion years or so (since photosynthesis first evolved.)
JayK
1 / 5 (2) Jan 15, 2010
@PinkElephant,

That should be very falsifiable, would you not agree? A single instance of finding a photosynthesis process that is more efficient than anything the plant world has evolved would quickly prove your hypothesis of optimization incorrect, right? Well, it appears from the article itself that that is exactly what has been developed, a protein that is key to the process of photosynthesis that makes it bond to more CO2 and less oxygen that would give the plants a new advantage.

But in general, why do you think evolution leads to the most optimal organisms or processes? Wouldn't the optimal process only be viable for limited environments for that organism or process? For instance, plants growing along the equator have less need for maximum efficiency photosynthesis processes than plants living closer to the poles, due to availability of direct sunlight.
Ronan
not rated yet Jan 15, 2010
Parsec: That's an interesting idea (Rubisco acting as an oxygen-tamer, so to speak), but I don't think it makes sense. There are several types of plants that go out of their way to make sure that oxygen doesn't come anywhere near Rubisco so that they can conduct more efficient carbon fixation (CAM and C4 plants; I recommend looking them up on Wikipedia, they're both quite interesting), and as far as I know (which is not, so to speak, very far), they don't have any odd oxidative-damage repair pathways that aren't found in normal plants. Odd as it seems, Rubisco may just be an old relic from pre-oxygen days that evolution has never tampered with much, despite its inefficiencies.

And PinkElephant, do you know whether or not the amount of carbon dioxide available in the air is normally the limiting factor for plant growth (I don't, I haven't looked into this deeply)? If that's the case, then your worry about runaway carbon sequestration would have some fangs; otherwise, though...
Ronan
not rated yet Jan 15, 2010
I'm sorry, I just realized there's an (obvious) logical error in my previous post; even if carbon dioxide isn't the limiting factor, the amount of time a plant can afford to keep its stomata open (due to the problem of water loss) is, and a more efficient Rubisco protein would allow a plant to preserve water within itself much better. You would get more plant growth, maybe much more plant growth, with this modified protein--just like, y'know, the article above pointed out. Bad unobservant Ronan.
JayK
1 / 5 (2) Jan 15, 2010
Ah, I just came up with an analogy that might explain my position on optimization in evolution:

Two guys are out walking in the woods when a bear starts coming after them. The first guy says "I don't think we can run fast enough to get away!" and the other answers "I don't have to run fast enough to get away, I just have to run faster than you."

In essence, that is the optimization issue. Organisms don't have to be optimum, they just have to be good enough to escape death long enough to pass on their successful traits.
PinkElephant
not rated yet Jan 15, 2010
@Ronan,

There's this widespread notion that increasing the amount of carbon in the atmosphere, should have a fertilizing effect on plant growth. So, while I haven't delved into details, I would assume that carbon fixation is indeed an important factor.
PinkElephant
not rated yet Jan 15, 2010
@JayK

Well, it appears from the article itself that that is exactly what has been developed


No, it hasn't been. All they had developed so far, is a way to assemble that same (unaltered) protein in a test tube. They have yet to "optimize" the protein, then insert the altered gene into a plant to see what happens...

"I don't have to run fast enough to get away, I just have to run faster than you."


That's the whole point. Over time, there's a kind of arms race. I run a little faster than you, so you go extinct and I proliferate. Then someone else starts running faster than me: I go extinct, they proliferate. Over time, this results in highly optimized structures.

Your vital mistake is that you're failing to differentiate between features that are adaptive exclusively to a specific environment vs. those that are universally beneficial (i.e. important to survival independently of environment, within reasonable limits.)
DachpyarviIe
1 / 5 (3) Jan 25, 2010
"There work has been published in Nature'. I wouldn't trust this publication if I were you, the results have been 'adjusted' to fit the authors claims :)
I would like to see the raw data first before taking thsi seriously, surely there should be an effective control. They mucked up here, its a shame