Even though we think about the cells and organelles inside us that map them so well, it seems like there are still some surprises in store.
A team of researchers has just published a paper describing the amazing structure that exists in an organelle – hidden from plain sight for decades.
The organelle is called a peroxisome – a bubble-like membrane filled with a granular protein matrix called a lumen. It is not the most important cell machinery (not exactly the mitochondria or the nucleus) but these very small cell organs have major roles in breaking down and synthesizing molecules.
Inside the peroxisomes of plant cells, researchers were surprised to find vesicles – something we don’t think are organelles.
Peroxisomes float around the cells of all multicellular organisms that remove reactive molecules with oxygen and help break down fats. In humans and other mammals, they are only 0.1 micrometres – so small that despite having a high-powered microscope, it is not much to look at.
“Peroxisomes in cells in yeast and mammals are smaller than the resolution of light,” explains Zachary Wright, a biochemist at Rice University.
“With fluorescence microscopy, you could only see a dot. That’s the limit that light can do.”
But Wright was studying the plant Arabidopsis Thaliana As a graduate when he found unexpected formations within peroxism.
Arabidopsis, A kind of watercress, really has really large peroxisomes. In seedlings, they can be 9-12 micrometres, not only clearly visible under a microscope, but also large enough to peer inside them.
“Bright fluorescent protein, in combination with many large peroxisomes in it Arabidopsis, Made it much clearer and easier to see this, ”Wright said.
“I reviewed really old literature about peroxisomes from the 60’s, and found that they observed similar things and just didn’t understand them.”
Peroxisomes of four-day-old Arbidopsis thalia plant cells. (Zachary Wright / Rice University)
As you can see in the image above, the team found that in addition to the normal membrane we know, there are many other membranes inside the organelle – also known as vesicles.
These vesicles (green showing the membrane) float through the lumen (pink).
Vesicles are commonly used to transport molecules around a cell or inside an organelle. They keep the molecules securely in a watertight cocoon where they cannot react with other parts of the cell.
“By taking advantage of the benefits of Arabidopsis The system, “the team wrote in their new paper,” found our findings challenge the long-held view of peroxisomes as simple single-membrane organelles and could help address the fundamental questions of peroxisome function and evolution. “
However, we are convinced that the newly discovered peroxisome vesicles are also present in human cells and we will need to do more research to confirm what they are actually doing, the team has a few ideas.
“When you think of a conventional type of biochemical reaction, we only have a substrate in the aquatic environment of a cell that has a lumen – and a substrate that comes in contact with the enzyme; it doesn’t work as well if you find something like that.” Don’t hang in the water. ‘
“Therefore, if you can use this membrane to dissolve water-insoluble metabolites, and better penetrate lumen enzymes, it may present a general strategy for dealing with that type of metabolism more effectively.”
Research has been published in Nature Communications.
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