Hinge stiffness is a barrier to RNA folding |
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Authors: | Schlatterer Jörg C Kwok Lisa W Lamb Jessica S Park Hye Yoon Andresen Kurt Brenowitz Michael Pollack Lois |
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Institution: | 1 Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA 2 School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA |
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Abstract: | Cation-mediated RNA folding from extended to compact, biologically active conformations relies on a temporal balance of forces. The Mg2 +-mediated folding of the Tetrahymena thermophila ribozyme is characterized by rapid nonspecific collapse followed by tertiary-contact-induced compaction. This article focuses on an autonomously folding portion of the Tetrahymena ribozyme, its P4-P6 domain, in order to probe one facet of the rapid collapse: chain flexibility. The time evolution of P4-P6 folding was followed by global and local measures as a function of Mg2 + concentration. While all concentrations of Mg2 + studied are sufficient to screen the charge on the helices, the rates of compaction and tertiary contact formation diverge as the concentration of Mg2 + increases; collapse is greatly accelerated by Mg2 +, while tertiary contact formation is not. These studies highlight the importance of chain stiffness to RNA folding; at 10 mM Mg2 +, a stiff hinge limits the rate of P4-P6 folding. At higher magnesium concentrations, the rate-limiting step shifts from hinge bending to tertiary contact formation. |
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Keywords: | SAXS small-angle X-ray scattering WLC wormlike chain |
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