3n25

Publication Abstract from PubMed

In the study of rabbit muscle pyruvate kinase (M(1)-PYK), proline has previously been used as an osmolyte in an attempt to determine a role for pre-existing conformational equilibria in allosteric regulation. In this context, osmolytes are small molecules assumed to have no direct interaction with the protein. In contrast to its proposed role as an osmolyte, the structure of M(1)PYK-Mn-pyruvate-proline complex reported herein demonstrates that proline binds specifically to the allosteric site of M(1)-PYK. Therefore, this amino acid is an allosteric effector, rather than a benign osmolyte. Other compounds often used as osmolytes (polyethyleneglycol and glycerol) are also present in the structure, suggesting an interaction with the protein that would, in turn, prevent the usefulness of these compounds in the study of this and most likely other proteins. These findings highlight the need to verify that compounds used as osmolytes to perturb pre-existing conformational equilibrium do not directly interact with the protein, a consideration not commonly addressed in the past.

The pyruvate kinase model system, a cautionary tale for the use of osmolyte perturbations to support conformational equilibria in allostery.,Fenton AW, Johnson TA, Holyoak T Protein Sci. 2010 Jul 13. PMID:20629175^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.