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Hot! Hot! Hot! But How?

Ever been outside on a day so hot, you said to your friends, "I feel like I’m melting"? Well, of course you were exaggerating. But there are microbes called thermophiles <ther-mo-files>, or heat-lovers, that live in temperatures so hot, the microbes could actually melt if they hadn’t developed tricks and tools to handle such extreme heat.

Special Enzymes

ProteinThermophiles have certain proteins, or enzymes, that are specially geared to working in high temperatures even as hot at 284° F (140° C). Keep in mind that water boils at 212° F (100° C). The normal-temperature proteins and enzymes in your body would start unfolding and breaking apart long before it got as hot as 284° F.

You see, proteins are strings of molecules called amino <ah-mee-no> acids (imagine a string of pearls with each pearl representing an amino acid). But for proteins to work right, their amino acid strings can’t just stretch out in a line.

Folded proteinThey have to be twisted and folded in just the right three-dimensional patterns (imagine bunching that pearl necklace up in your hand). High heat can cause these 3-D structures to unfold and the links holding the pattern together to break. And when they unfold, enzymes no longer work right.

Enzymes in thermophiles are called extremozymes <ex-treem-oh-zimes>. One thing that these extremozymes do to hold their 3-D shapes together in high heat is folding themselves tighter than normal temperature enzymes do. As you know, a tight knot in your shoelace is harder to get out than a loose one. Also, lots of chemical bonds formed between amino acids on the outer surfaces of extremozymes help keep these proteins intact and folded just right. These bonds act as fasteners holding together the shape of the enzymes.

Another trick is having a smaller amount of the amino acid glycine <gly-seen> than normal-temperature proteins have. Of the 20 different amino acids that make proteins, glycine is the second most commonly found in regular proteins. It helps them be flexible and bend a bit. Having less glycine makes extremozymes more rigid and sturdier.

One really cool tool hyperthermophiles use to keep their enzymes working right is a special type of fix-it protein called "chaperonin" <shap-er-oh-nin>. These chaperonin proteins fix enzymes beginning to fall apart by latching onto them and refolding them back into their active patterns—sort of like a microscopic back doctor except that chaperonins put the kinks back in instead of taking them out.

 

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