Allosteric transition and binding of small molecule effectors causes curvature change in central β-sheets of selected enzymes.
A quantitative description of allosteric transition remains a significant science challenge. Many allosteric enzymes contain a central β-sheet in their catalytic domain. When an allosteric protein undergoes the transition between T (tense) and R (relaxed) allosteric states, this central β-sheet undergoes a conformational change. A traditional method of measuring this change, the root mean square deviation (RMSD), appears to be inadequate to describe such changes in meaningful quantitative manner. We designed a novel quantitative method to demonstrate this conformational transition by measuring the change in curvature of the central β-sheet when enzymes transition between allosteric states. The curvature was established by calculating the semiaxes of a 3-D hyperboloid fitted by least squares to the Cα atomic positions of the β-sheet. The two enzymes selected for this study, fructose 1,6-bisphosphatase (FBPase) from pig kidney and aspartate carbamoyltransferase (ATCase) from E. coli, showed while transitioning between the allosteric states (T ⇔ R) a notable change in β-sheet curvature (∼5%) that results in a large lateral shift at the sheet's edge, which is necessary to convey the signal. The results suggest that the β-sheet participates in storing elastic energy associated with the transition. Establishing a tentative link between the energetics of the β-sheet in different allosteric states provides a more objective basis for the naming convention of allosteric states (tense or relaxed), and provides insight into the hysteretic nature of the transition. The approach presented here allows for a better understanding of the internal dynamics of allosteric enzymes by defining the domains that directly participate in the transition.
Tolonen
Ellen
E
Department of Chemistry, University of Texas, El Paso, TX 79968, USA.
Bueno
Brenda
B
Kulshreshta
Sanjeev
S
Cieplak
Piotr
P
Argáez
Miguel
M
Velázquez
Leticia
L
Stec
Boguslaw
B
D000494:Allosteric Regulation; D000818:Animals; D001221:Aspartate Carbamoyltransferase / Q000737:chemistry*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology; D006597:Fructose-Bisphosphatase / Q000737:chemistry*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D011487:Protein Conformation; D013552:Swine
D001221:Aspartate Carbamoyltransferase; D006597:Fructose-Bisphosphatase