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UNSTRUCTURED NASCENT-CHAIN SEGMENTS GENERATE PICONEWTONS OF FORCE THAT ARE TRANSMITTED THROUGH THE PEPTIDE BACKBONE TO THE RIBOSOME P-SITE
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Fritch, Ben R
Master of Science
Date of Defense:
April 15, 2017
Dr. Edward O'Brien, Thesis Advisor
Dr. Scott Showalter, Committee Member
Dr. Gerald Knizia, Committee Member
Mechanical forces acting on the ribosome can alter the speed of protein synthesis. These forces have diverse origins including the SecA motor protein that aids in protein translocation, and co-translational protein folding, indicating that co translational processes can regulate translation through the medium of mechanochemistry. Using in situ experimental measurements of changes in nascent chain extension in the exit tunnel, in conjunction with all-atom and coarse-grained computer simulations, we demonstrate that when a nascent chain is lengthened, its unstructured segments outside the ribosome exit tunnel can generate piconewtons of force that is transmitted through the polypeptide backbone to the ribosome’s catalytic core. Since all nascent protein segments start out as unfolded structural ensembles, these results indicate that a universal pulling force is present during protein synthesis that increases with increasing protein length.
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