Allosteric Mechanism of Pyruvate Kinase from Leishmania mexicana Uses a Rock and Lock Model

• Published in: The Journal of biological chemistry 2010-04, Vol.285 (17), p.12892-12898
• Main Authors: Morgan, Hugh P., McNae, Iain W., Nowicki, Matthew W., Hannaert, Véronique, Michels, Paul A.M., Fothergill-Gilmore, Linda A., Walkinshaw, Malcolm D.
• Format: Article
• Language: English
• Subjects: Allosteric Regulation - physiology; Animals; Enzymes/Allosteric Regulation; Enzymes/Mechanisms; Enzymology; Leishmania mexicana; Leishmania mexicana - enzymology; Metabolism/Glycolysis; Methods/X-ray Crystallography; Models, Chemical; Models, Molecular; Organisms/Parasite; Protein Structure and Folding; Protein Structure, Tertiary; Protozoan Proteins - chemistry; Protozoan Proteins - metabolism; Pyruvate Kinase - chemistry; Pyruvate Kinase - metabolism; Thermodynamics
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109.079905

Allosteric regulation provides a rate management system for enzymes involved in many cellular processes. Ligand-controlled regulation is easily recognizable, but the underlying molecular mechanisms have remained elusive. We have obtained the first complete series of allosteric structures, in all possible ligated states, for the tetrameric enzyme, pyruvate kinase, from Leishmania mexicana. The transition between inactive T-state and active R-state is accompanied by a simple symmetrical 6° rigid body rocking motion of the A- and C-domain cores in each of the four subunits. However, formation of the R-state in this way is only part of the mechanism; eight essential salt bridge locks that form across the C-C interface provide tetramer rigidity with a coupled 7-fold increase in rate. The results presented here illustrate how conformational changes coupled with effector binding correlate with loss of flexibility and increase in thermal stability providing a general mechanism for allosteric control.