Morpheeins--a new structural paradigm for allosteric regulation.
Classic models for the allosteric regulation of protein function consider an equilibrium among protein structures of constant oligomeric multiplicity. The morpheein (mor-phee'-in) concept expands this model to include a dynamic equilibrium of protein structures wherein a protein monomer can exist in more than one conformation and each monomer conformation dictates a different quaternary structure of finite multiplicity and different functionality. The morpheein concept provides a new framework for understanding allosteric regulation, kinetic cooperativity and hysteresis. Porphobilinogen synthase constitutes a prototype morpheein ensemble comprising several interconverting quaternary structure isoforms; one monomer conformation dictates assembly of a high-activity octamer, whereas an alternative monomer conformation dictates assembly of a low-activity hexamer. It is proposed here that the behavior of some other allosteric enzymes reflect dynamic morpheein equilibrium systems and six candidate proteins are enumerated.
Jaffe
Eileen K
EK
BioMolecular Structure and Function Group, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA. Eileen.Jaffe@fccc.edu
D000494:Allosteric Regulation; D007700:Kinetics; D008956:Models, Chemical; D000623:Porphobilinogen Synthase / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D013329:Structure-Activity Relationship
D000623:Porphobilinogen Synthase