Labels

Copper Proteins & Succulents

This site isn't all talk and no walk. I am a real scientist, though far far from a biologist.

My main line of research is in dicopper proteins, or more specifically Type III Coupled Binuclear Copper (CBC) proteins. The coupled comes from the copper atoms being antiferromagnetically coupled giving a silent EPR spectrum (but that doesn't matter to you). All you need to know is that it somehow wound up in the name. Binuclear means dicopper or two copper ions in the active site. The copper ions are coordinated by three histidine residues each and a bridging oxygen ligand.

Nearly half of all proteins have got metal in them (metalloproteins) and copper is pretty common because of its high natural abundance and redox activity. The chart below should help you navigate the proteins that I work with. Proteins > Metalloproteins > Type III Cu proteins. Ding!Ding!Ding!

Figure via creative commons article
These CBC proteins do stuff like brown your fruit, form skin pigmentation, and activate and transport oxygen (just like hemoglobin in humans). Prime examples are catechol oxidases, tyrosinases, and haemocyanins. These are found in anthropods (spiders, insects, crabs, lobsters, crayfish, shrimp, and prawns...etc.) and mollusks (squid, octopus, snails, slugs, oysters, muscles, clams...etc.). Copper proteins are found in people too! Tyrosinase is involved in pigment formation, meaning that your skin, hair, and eye color are all thanks to copper proteins!

Figure via creative commons article
There's a dark side to copper proteins too, which is why research is so important. They've been implicated in neurodegenerative diseases like Alzheimer's, Parkinson's, and ALS--but these are copper proteins with problems.

So I bet you're wondering, how does this relate to succulents? Can this girl really relate everything back to those glorious plants?

Why, yes I can.

Succulents and Copper Proteins


 Plastocyanin
Succulents undergo CAM photosynthesis, which you can read about here, but any plant that undergoes photosynthesis may need a little help from a copper protein friend. Plastocyanin is a Type I blue copper protein (not a CBC protein like the ones I study) that is involved in the electron transport process during photosynthesis. It ferries electrons from the cytochrome complex to Photosystem I. You can read more about the process here.
Plastocyanin acitve site: you can see that copper atom ball
If a plant has a deficiency of copper ions, then photosynthesis will be shut down. The plastocyanin protein cannot function without its copper cofactor. You will see signs of copper deficiency in your plant if it starts growing dark green leaves with dead spots. The succulent will eventually die if left untreated. What can affect whether your succulent has enough copper? The soil pH! Read my post about how soil pH affects the macro and micronutrients (copper is a micronutrient) in the soil here.

But--as you should all know by now--succulents are hardy creatures! Some plants near a copper mine were found to have adapted to withstand normally toxic levels of copper (5000–16800 mg kg−1). One of them was Sedum sediforme, a succulent native to southwestern Europe with glaucous blue leaves. Amazing, huh?

Sedum sediforme in bloom. Photo via wikimedia.

Cu/Zn SOD protein
Another kind of copper protein (okay, it's not just copper, it's zinc and copper) is the Cu/Zn SOD protein. It is one of the most important reactive oxygen species (ROS) scavengers out there and is found in plant cytosol, chloroplasts, and peroxisomes. 

Above: Chloroplast plush toys! The stacks of disks (thylakoids) are called grana (sing. granum). Buy these cuties here.

ROS can damage DNA and harm your plant by causing mutations, so it is important that these oxygen radicals be turned into the less harmless hydrogen peroxide. That's what the Cu/Zn SOD protein can do. One study looked at Sedum alfredii to see how Cu/Zn SOD proteins could help the plant cope with heavy metal stress. Read more here.

Once again, having just the right amount of copper is necessary for everything to work the right way. Too much or too little could spell disaster for any living organism. Too little could lead to the problems listed above. Too much could cause overproduction of hydrogen peroxides that undergo the Fenton reaction to make free hydroxyl radical species...which can also cause DNA damage.

It is NOT the same as the human Cu/Zn SOD1 which has been implicated in ALS. Actually, it is the misfolding of the human Cu/Zn SOD1 protein that we think leads to aggregation that could possibly cause familial ALS (we're really not sure what's happening with ALS and other FTD diseases. However, lots of research is being done involving more than 100 different single-point mutations, metal imbalances, and other possible possibilities.) However, plants can help researchers possibly find a way to figure out how to prevent this misfolding. You see, if a plant accumulates too many misfolded proteins in the chloroplasts, it will send a distress signal that triggers other proteins (chaperones) to come repair the damage. Unlike in humans where we accumulate more and more of the misfolded proteins. You can read more about ALS plant-inspired cures here.

Aloe Vera as an anti-Tyrosinase Skincare Treatment
As was briefly mentioned above, Tyrosinase is a Type III dicopper protein (this I actually study) that is able to perform catechol oxidation in the formation of melanin. Inhibiting tyrosinase could lead to treatments for skin hyperpigmentation caused by acne scars and sun exposure. Currently, topical treatments for dark spots have unsavory side effects, so dermatologists and the cosmetics industry are looking for more desirable alternatives. Enter Aloe Vera, the natural beauty product of choice for Cleopatra, known by many as the apothecary in a plant. 

Aloe vera: cut this bad boy up and slather that on your face at night for a au naturel facial
Aloe vera contains Aloesin [2-acetonyl-8-b-D-glucopyranosyl-7-hydroxy-5-methylchromone] which has been shown to reduce pigmentation by 34% on the fifteen people they studied (Choi et al., 2002). So how does this work? The aloesin interacts by hydrogen bonding with amino acids on the Tyrosinase: His244, Thr261, and Val283. This prevents the Tyrosinase from doing its job, that is, forming melanin, and getting you back to being blemish free.

Aloesin

Conclusion
Thanks for reading a little bit about how copper proteins work in succulents! I hope you learned a few things today and got a little glimpse into my world of proteins. Succulents are amazing and so are copper proteins (copper proteins rule!) For more succulent fun, please hit that subscribe button!

Email Post
Labels:

Comments

Post a Comment

Popular Posts