Scientists solve the mysterious organ behind the pyrenoid

Born with algae Chlamydomonas reinhardtii. The loan. Image: He և others

Carbon is one of the major building blocks of life on Earth. It is abundant in the atmosphere of our planet, where it is found in the form of carbon dioxide. Carbon travels to terrestrial bodies mainly through photosynthesis, which includes carbon dioxide in sugars, which serve as components of important biomolecules, the global fuel chain of fuel. About a third of this process is carried out worldwide by unicellular algae living in the oceans (the rest is done by plants).

The enzyme that carries out the first step in the reaction of assimilating carbon dioxide into sugar is a large protein called Rubisco, which is made up of eight identical small subunits and eight identical large subunits arranged symmetrically together. All parts of this collection called the Holoenzyme work together to fulfill Rubisco’s enzymatic duty. Rubisco’s level of activity, և by extension, plants և algae can grow, limited by the availability of carbon dioxide. Free carbon dioxide may be scarce in water, so aquatic algae such as Chlamydomonas reinhardtii: sometimes they struggle to get Rubisco to run at full capacity. To counteract this, these algae developed a special structure called a pyrenoid to supply Rubisco with concentrated carbon dioxide. The pyrenoid is so powerful that almost all algae on the planet have one. It is believed that different species of algae have developed their own structure.

“The defining feature of the pyrenoid is the matrix, a giant liquid-like concentrate that contains almost all of the cell Rubicon,” explains Jon Onikas, an assistant professor at Princeton Molecular Biology.

Rubisco և EPYC1 Pyrenoid Matrix:

Rubisco (teal) binds և is assembled via EPYC1 (orange) into a pyrenoid matrix. Sub-head. Princeton researchers Shan Hay and Martin Jon Onikas and their colleagues have discovered how Rubisco’s holoenzymes form to form a liquid algae pyreneoid matrix, an organ that mediates the absorption of carbon dioxide into sugars. A detailed study of the group’s results was published in the November 23, 2020 issue of the journal Nature Plants. The loan. Image: He և others.

Rubisco is the main component of the pyrenoid matrix, but not the only one. In 2016, Jonikas Laboratory discovered another abundant protein in the pyrenoid called EPYC1. In his 2016 In the article, Jon Onikas’s group showed that EPYC1 is linked to Rubisco և helps Rubisco focus on the pyrenoid. Researchers have theorized that EPYC1 works like a molecular glue to bind Rubisco anticoagulants together. Postdoc Shan He, along with his colleagues at Jon Onikas Lab և Germany, Singapore և England, set out to test this theory.

“In this work, we show that this is really the case,” says Jon Onikas, “showing that EPYC1 has five binding sites for Rubisco, allowing it to ‘link’ to Rubisco holoenzymes.” »:

EPYC1 is a weakly structured, expanded protein, հինգ its five Rubisco binding sites are evenly distributed throughout its length. The researchers found that Rubisco has eight EPYC1 linking sites that are evenly distributed across the globular surface. Computer modeling has shown that a weakly structured, flexible EPYC1 protein can establish multiple bonds with a single Rubisco holoenzyme or bridge the gap. Thus, EPYC1 pushes Rubisco to assemble into a pyrenoid matrix.

While this is a satisfying explanation for how the matrix is ​​assembled, it is a mystery. Other proteins must be able to access Rubisco to restore it when it breaks down. If the EPYC1-Rubisco network is solid, it may block the access of these proteins to Rubisco. However, his colleagues found that the interaction of EPYC1 with Rubisco is quite weak, so although the two proteins can make many contacts with each other, these contacts exchange quickly.

“This allows EPYC1 և Rubisco to pass side by side while remaining in a densely packed concentrate, allowing other pyreneoid proteins to enter Rubisco as well,” ik Onikas notes. “Our work solves the long-standing mystery of how Rubisco is stored in the pyrenoid matrix.”

Soil crops do not have pyrene, scientists believe that the development of a pyrene-like structure in crops can stimulate their growth rate. Understanding how pyrenodes are collected in algae is a significant step in such an effort.

“He and his colleagues are doing a very good molecular study of the protein-protein interactions of EubYc1, a small subdivision of Rubisco,” said Dr. James Ames Moroni, a professor of biology at Louisiana State University’s Department of Biology. և Algae.

“This work is encouraging for researchers trying to incorporate pyrene-like structures into plants to improve photosynthesis,” he added.

In a world plagued by hunger and disease, we can use all our stimuli.

Reference. Shan He, Hui-Ting Chou, Dorin Matisse, Tobias Wunder, Maurice T. Meyer, Nicky Atkinson, Antonio Martinez-Sanchez, Philip D. Ff Effrey, Sarah A. Port, Weronika Patena, Guanhua He, Vivian K. Chen, Frederick M. Hughson, Alistair J. McCormick, Oliver Mueller-Cajar, Benjamin D. Engel, Zhiheng Yu and Martin C. Jonikas, 23 November 2020, Plants of nature,
DOI: 10.1038 / s41477-020-00811-y:

Financing. The work described here was supported by grants from the National Science Foundation (No. IOS-1359682 և MCB-1935444), the National Institutes of Health (No. DP2-GM-119137), the Simmons Foundation, and the MCJ of the Howard Hughes Medical Institute. (No. 55108535); to BDE by Deutsche Forschungsgemeinschaft (EN 1194 / 1-1 as part of FOR2092); to OM-C: By the Ministry of Education (MOE Singapore) Tier 2 (No. MOE2018-T2-2-059); To UBA և NA կողմից by the Biotechnology և Biological Sciences Research Council of the United Kingdom (No. BB / S015531 / 1) և Leverhulme Trust (No. RPG-2017-402). to FMH by NIH (R01GM071574); to SAP through the Deutsche Forschungsgemeinschaft Scholarship (No. PO2195 / 1-1); և VKC training grant from the National Institute of General Medical Sciences of the Institute of Health (No. T32GM007276).

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