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A new study by scientists at Rice University and elsewhere examinesstructures of proteins that not only twist and turn themselves intoknots, but also form slipknots that, if anybody could actually seethem, might look like shoelaces for cells. Proteins that serve the same essential functions in speciesseparated by more than a billion years of evolution often displayremarkable similarities. Joanna Sulkowska, a postdoctoralresearcher at the Center for Theoretical Biological Physics (CTBP)at the University of California at San Diego, said these"strongly conserved" parts of proteins are especiallycommon among those folds and hinges responsible for the knottedportions of a protein strand. Sulkowska, co-first author of a new paper in the Proceedings of the National Academy of Sciences , works in the lab of her co-author, José Onuchic, Rice'sHarry C. and Olga K. Wiess Chair of Physics and a professor ofphysics and astronomy, chemistry, biochemistry and cell biology.Sulkowska expects to spend part of her year at CTBP when it movesits base of operation to Rice's BioScience Research Collaborativethis year. She said slipknotted proteins, while rare, have been found inproteins that cross membrane barriers in cells. These transmembraneproteins stick through the cell membrane like pins in a pin cushionand help the cell sense and respond to its environment. "Theslipknot is surprisingly conserved across many different families,from different species: bacteria, yeast and even human,"Sulkowska said. "They have really different evolutionarypathways, yet they conserve the same kind of motif. We think theslipknot stabilizes the location of the protein inside themembrane." Although a typical protein folds in a fraction of a second,researchers can see from simulations that knotted and slipknottedproteins would take longer to reach their folded structures thanwould unknotted proteins. Sulkowska said the extra effort to foldinto knotted shapes must have a biological payoff or nature wouldhave selected an easier path. Finding the payoff is no easy task, but there are genomic clues.For instance, she said researchers suspect that "activesites" that control the folding pattern for knotted proteinsoften wind up inside the knotted structures after folding is complete. It's possible,she said, that knotted proteins also have chaperone proteins thathelp the process along. Another mystery to be solved is how thebody degrades knotted proteins; breaking down misfolded proteins isa normal function for healthy cells, and breakdowns in this processhave been implicated in diseases like Alzheimer's and Parkinsons. Sulkowska, whose interest in knots extends to the macro realms ofsailing and climbing, is sure there's a good reason for all thatshe and Onuchic are seeing. "This is a new field, but wealready know from experience how useful knots are," she said."They're almost everywhere: in your shoes, in moving cargo, inphysics as part of string theory. Now we hope to make thisknowledge useful, maybe as a way to design new types of very stableproteins for disease treatment. "Evolution didn't redact these proteins," she said."They still fold, so they must have some function." Eric J. Rawdon of the University of St. Thomas, St. Paul, Minn., isco-first author. Co-authors include Kenneth Millett of theUniversity of California at Santa Barbara and Andrzej Stasiak ofthe University of Lausanne, France. The National Science Foundation, through CTBP, and the SwissNational Science Foundation supported the research. I am an expert from constant-current-leddriver.com, while we provides the quality product, such as Dimmable Led Driver Manufacturer , Halogen Lamp Electronic Transformer, 12 Volt Led Driver,and more.
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