Hidden Structure Found in Essential Metabolic Machinery
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Hidden structure found in essential metabolic machinery:
In his first year of graduate school, Rice University biochemist Zachary Wright discovered something hidden inside a common piece of cellular machinery that's essential for all higher order life from yeast to humans.
What Wright saw in 2015 - subcompartments inside organelles called peroxisomes - is described in a study published today in Nature Communications.
"This is, without a doubt, the most unexpected thing our lab has ever discovered," said study co-author Bonnie Bartel, Wright's Ph.D. adviser and a member of the National Academy of Sciences. "This requires us to rethink everything we thought we knew about peroxisomes."
Peroxisomes are compartments where cells turn fatty molecules into energy and useful materials, like the myelin sheaths that protect nerve cells. In humans, peroxisome dysfunction has been linked to severe metabolic disorders, and peroxisomes may have wider significance for neurodegeneration, obesity, cancer and age-related disorders.
[...] The peroxisomes he was viewing were up to 100 times larger. Scientists aren't certain why peroxisomes get so large in Arabidopsis seedlings, but they do know that germinating Arabidopsis seeds get all of their energy from stored fat, until the seedling leaves can start producing energy from photosynthesis. During germination, they are sustained by countless tiny droplets of oil, and their peroxisomes must work overtime to process the oil. When they do, they grow several times larger than normal.
"Bright fluorescent proteins, in combination with much bigger peroxisomes in Arabidopsis, made it extremely apparent, and much easier, to see this," Wright said.
But peroxisomes are also highly conserved, from plants to yeast to humans, and Bartel said there are hints that these structures may be general features of peroxisomes.
"Peroxisomes are a basic organelle that has been with eukaryotes for a very long time, and there have been observations across eukaryotes, often in particular mutants, where the peroxisomes are either bigger or less packed with proteins, and thus easier to visualize," she said. But people didn't necessarily pay attention to those observations because the enlarged peroxisomes resulted from known mutations.
Journal Reference:
Zachary J. Wright, Bonnie Bartel. Peroxisomes form intralumenal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis [open], Nature Communications (DOI: 10.1038/s41467-020-20099-y)
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