1. Structural and thermodynamic analyses of the β-to-α transformation in RfaH reveal principles of fold-switching proteins
- Author
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Philipp K. Zuber, Tina Daviter, Ramona Heißmann, Ulrike Persau, Kristian Schweimer, and Stefan H. Knauer
- Subjects
Protein Folding ,General Immunology and Microbiology ,Escherichia coli Proteins ,General Neuroscience ,Escherichia coli ,Trans-Activators ,Thermodynamics ,General Medicine ,Peptide Elongation Factors ,General Biochemistry, Genetics and Molecular Biology ,Transcription Factors - Abstract
The two-domain protein RfaH, a paralog of the universally conserved NusG/Spt5 transcription factors, is regulated by autoinhibition coupled to the reversible conformational switch of its 60-residue C-terminal KOW domain between an α-hairpin and a β-barrel. In contrast, NusG/Spt5-KOW domains only occur in the β-barrel state. To understand the principles underlying the drastic fold switch in RfaH, we elucidated the thermodynamic stability and the structural dynamics of two RfaH- and four NusG/Spt5-KOW domains by combining biophysical and structural biology methods. We find that the RfaH-KOW β-barrel is thermodynamically less stable than that of most NusG/Spt5-KOWs and we show that it is in equilibrium with a globally unfolded species, which, strikingly, contains two helical regions that prime the transition towards the α-hairpin. Our results suggest that transiently structured elements in the unfolded conformation might drive the global folding transition in metamorphic proteins in general.
- Published
- 2022