Magnetic Resonance
Magnetic Resonance
Magnetic Resonance
Preprints
https://doi.org/10.5194/mr-2020-37
https://doi.org/10.5194/mr-2020-37

  04 Jan 2021

04 Jan 2021

Review status: this preprint is currently under review for the journal MR.

Fragile protein folds: Sequence and environmental factors affecting the equilibrium of two interconverting, stably folded protein conformations

Xingjian Xu1,2, Igor Dikiy1,a, Matthew R. Evansb, Leandro P. Marcelino1,3, and Kevin H. Gardner1,3,4 Xingjian Xu et al.
  • 1Structural Biology Initiative, CUNY Advanced Science Research Center, New York, NY, USA
  • 2Ph.D. Program in Biochemistry, The Graduate Center, CUNY, New York, NY, USA
  • 3Department of Chemistry and Biochemistry, City College of New York, New York, NY, USA
  • 4Biochemistry, Chemistry and Biology Ph.D. Programs, The Graduate Center, CUNY, New York, NY, USA
  • acurrent address: Regeneron Pharmaceuticals, Tarrytown, NY, USA
  • bcurrent address: Acclaim Physician Group, Inc. Fort Worth, TX, USA

Abstract. Recent research on fold-switching metamorphic proteins has revealed some notable exceptions to Anfinsen's hypothesis of protein folding. We have previously described how a single point mutation can enable a well-folded protein domain, one of the two PAS (Per-ARNT-Sim) domains of the human ARNT (aryl hydrocarbon receptor nuclear translocator) protein, to interconvert between two conformers related by a slip of an internal beta-strand. Using this protein as a test case, we advance the concept of a fragile fold, a protein fold that can reversibly rearrange into another fold that differs by a substantial number of hydrogen bonds, entailing reorganization of single secondary structure elements to more drastic changes seen in metamorphic proteins. Here we use a battery of biophysical tests to examine several factors affecting the equilibrium between the two conformations of the switching ARNT PAS-B Y456T protein. Of note, we find that factors which impact the HI loop preceding the shifted I(beta)-strand affect both the equilibrium levels of the two conformers and the denatured state which links them in the interconversion process. Finally, we describe small molecules that selectively bind to and stabilize the wildtype conformation of ARNT PAS-B. These studies form a toolkit for studying fragile protein folds and could enable ways to modulate the biological functions of such fragile folds, both in natural and engineered proteins.

Xingjian Xu et al.

Status: open (until 06 Feb 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Xingjian Xu et al.

Xingjian Xu et al.

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Short summary
While most proteins adopt a single well-folded structure, several are known which interconvert among two or more conformations. Here we examine one system which is in equilibrium between two folds differing by a +3 shift in beta-strand register, describing sequence and environmental factors that bias the populations of the two structures. Notably, small molecule binding shifts the equilibrium, setting ways to artificially control natural or engineered proteins with this domain.