title: Identification of the allosteric regulatory site of insulysin.
abstract: BACKGROUND
  Insulin degrading enzyme (IDE) is responsible for the metabolism of insulin and plays a role in clearance of the Aβ peptide associated with Alzheimer's disease. Unlike most proteolytic enzymes, IDE, which consists of four structurally related domains and exists primarily as a dimer, exhibits allosteric kinetics, being activated by both small substrate peptides and polyphosphates such as ATP.
  
  
  RESULTS
  The crystal structure of a catalytically compromised mutant of IDE has electron density for peptide ligands bound at the active site in domain 1 and a distal site in domain 2. Mutating residues in the distal site eliminates allosteric kinetics and activation by a small peptide, as well as greatly reducing activation by ATP, demonstrating that this site plays a key role in allostery. Comparison of the peptide bound IDE structure (using a low activity E111F IDE mutant) with unliganded wild type IDE shows a change in the interface between two halves of the clamshell-like molecule, which may enhance enzyme activity by altering the equilibrium between closed and open conformations. In addition, changes in the dimer interface suggest a basis for communication between subunits.
  
  
  CONCLUSIONS
  Our findings indicate that a region remote from the active site mediates allosteric activation of insulysin by peptides. Activation may involve a small conformational change that weakens the interface between two halves of the enzyme.
authors: Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Lexington, Kentucky, United States of America.
authors: Nicholas
authors: N
authors: Noinaj
authors: Sonia K
authors: SK
authors: Bhasin
authors: Eun Suk
authors: ES
authors: Song
authors: Kirsten E
authors: KE
authors: Scoggin
authors: Maria A
authors: MA
authors: Juliano
authors: Luiz
authors: L
authors: Juliano
authors: Louis B
authors: LB
authors: Hersh
authors: David W
authors: DW
authors: Rodgers
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D000494:Allosteric Regulation; D000495:Allosteric Site; D000818:Animals; D018360:Crystallography, X-Ray; D007339:Insulysin / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D013058:Mass Spectrometry; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D051381:Rats; D013050:Spectrometry, Fluorescence
chemical_list: D008024:Ligands; D050505:Mutant Proteins; C045674:2',3'-O-(2,4,6-trinitro-cyclohexadienylidine)adenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D007339:Insulysin