Scientists capture atomic level snapshots how key enzyme modifies - signaling proteins
Scientists have captured atomic level snapshots showing how a key enzyme modifies a protein involved in the transformation of genes on or off within cells. Understanding this process is particularly important when cells are first taking specialist identities such as nerve cells, muscle, skin, and so forth-helps explain how complex organisms can result from a number finished genes. The research, published in Nature Chemical Biology also identifies links between defects of this particular enzyme and certain cancers, potentially pointing to new targets for cancer drugs.
"Our work describes the structure and function of an important enzyme called Rumi, adding a glucose molecule to several signaling proteins to modify their activities," said the lead author of the study , Huilin Li, a biologist at the US department of Brookhaven National Laboratory for energy and the University of Stony Brook. "One of these target proteins, called Notch is the main receptor which controls the development of multicellular organisms. It plays an important role in the functioning of cells detect their neighbors, and by controlling the expression of the gene determines which cells must develop into different types and how much they have to grow as a master controller. "
Notch is also known to be a tumor suppressor. But its action is much more complicated than a simple on and off. It is a protein chain which spans the cell membrane with 3D complicated folding which 36 repeat "beads on a necklace" folds each of which may be modified in various ways to affect the function of the protein.
"We wanted to understand the structure of Notch on different types of change," said Li, who worked with Robert Haltiwanger and Hideyuki Takeuchi, biochemists at Stony Brook University at the time of experience now at the University of Georgia.
Picking up on recent findings that the enzyme modification called Rumi Notch is necessary for the development of animals and various Rumi mutants are related to a form of hyperpigmentation of the skin known as disease Dowling- Degos (made by scientists at Baylor College of Medicine and the University of Bonn, Germany), the Li group became focused on this particular enzyme. The study of Rumi-Notch interaction at the molecular level could help scientists understand the mechanisms of disease, and may even lead to the design of drugs against these diseases.
Background knowledge directs the precision study
Before the study, scientists already knew that Rumi modifies Notch by adding the protein to glucose molecules. There are other examples of proteins modified by other simple sugars, but Rumi is the first enzyme known to specifically add glucose.
Previous research had also revealed that the first glucose added by Rumi are essential for Notch signaling. "Without the glucose molecules, Notch can not take bending 3D right to mature in a functional receptor, and therefore can not work," said Li.
"Also, because Notch is known for be a tumor suppressor, the essential role of Rumi in Notch activation suggests that Rumi could be a tumor suppressor as well. If a chemical biologist wants to design drugs that affect this process, he or she would need to know the mechanism complex enzymatic reactions, "said Li.
"We decided to do just that to know the characteristics of the Notch protein Rumi research and how it puts a sugar (glucose) about it."
Details enzyme-protein interaction
Li's team studied samples of a version of the fruit fly from Rumi in complex with a Notch "substitute", a human protein with a notch-like fold which has been provided by Haltiwanger.
"It was very difficult to obtain sufficient samples," said Yu Hongjun, a postdoctoral researcher working with Li and first author of the article, noting that proteins are very small crystals with difficult to solve the structure. But finally, using intensely bright beams of X-rays at the National Synchrotron Radiation Source (NSLS) at Brookhaven and the Advanced Photon Source (APS) at Argonne Laboratory, both National Office DOE user facilities sciences, they collected sufficient data on the arrangement of atoms in proteins. They averaged data from multiple crystals to generate stronger signals, and used computers to reconstruct 3D images of how Notch Rumi parts and assemble.
The scientists found that Rumi recognizes a sequence of six amino acids over a large number of repeat 36 folds of Notch. A hydrophobic patch with separate recognition sequence is also essential for the interaction. When Rumi binds the six-amino acid sequence "signature" that accepts the glucose molecule is precisely in the active site of Rumi in a "lock-and-key" conventionally. "Adding or removing even one amino acid from that signature sequence, it would be impossible for proteins to join such a way, preventing glucose from being added," Yu said.
These studies revealed how mutations linked to cancer Rumi alter key structural components that make inactive Rumi. "Our study suggests that mutated forms of Rumi could cause cancer because these mutant enzymes are unable to modify Notch. This, for the first time, links with Rumi cancers defects," said Li. Scientists point however, other complex changes in Notch probably also play a role.
"We are studying the details of the study to determine the impact of biomedical our new understanding could be," said Li. This includes thinking if drugs could be developed to affect the behavior of Notch by targeting specific sites on Rumi.
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