Heterogeneous side chain conformation highlights a network of interactions implicated in hysteresis of the knotted protein, minimal tied trefoil.
Hysteresis is a signature for a bistability in the native landscape of a protein with significant transition state barriers for the interconversion of stable species. Large global stability, as in GFP, contributes to the observation of this rare hysteretic phenomenon in folding. The signature for such behavior is non-coincidence in the unfolding and refolding transitions, despite waiting significantly longer than the time necessary for complete denaturation. Our work indicates that hysteresis in the knotted protein, the minimal tied trefoil from Thermotoga maritma (MTTTm), is mediated by a network of side chain interactions within a tightly packed core. These initially identified interactions include proline 62 from a tight β-like turn, phenylalanine 65 at the beginning of the knotting loop, and histidine 114 that initiates the threading element. It is this tightly packed region and the knotting element that we propose is disrupted with prolonged incubation in the denatured state, and is involved in the observed hysteresis. Interestingly, the disruption is not linked to backbone interactions, but rather to the packing of side chains in this critical region.
Departments of Chemistry and Biochemistry, University of California at San Diego (UCSD), La Jolla, CA USA.
David J
DJ
Burban
Center for Theoretical Biological Physics (CTBP) and Department of Physics, University of California at San Diego (UCSD), La Jolla, CA USA.|Center for Theoretical Biological Physics (CTBP) and Departments of Physics and Astronomy, Chemistry and Biochemistry and Cell Biology, Rice University, Houston, TX USA.
Ellinor
E
Haglund
Departments of Chemistry and Biochemistry, University of California at San Diego (UCSD), La Jolla, CA USA.
Dominique T
DT
Capraro
Departments of Chemistry and Biochemistry, University of California at San Diego (UCSD), La Jolla, CA USA.
Patricia A
PA
Jennings
D001426:Bacterial Proteins / Q000737:chemistry*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D017510:Protein Folding; D013816:Thermodynamics; D020124:Thermotoga maritima / Q000737:chemistry*
D001426:Bacterial Proteins