Identification of the allosteric regulatory site of insulysin

• Published in: PloS one 2011-06, Vol.6 (6), p.e20864-e20864
• Main Authors: Noinaj, Nicholas, Bhasin, Sonia K, Song, Eun Suk, Scoggin, Kirsten E, Juliano, Maria A, Juliano, Luiz, Hersh, Louis B, Rodgers, David W
• Format: Article
• Language: English
• Subjects: Activation; Adenosine Triphosphate - analogs & derivatives; Adenosine Triphosphate - metabolism; Allosteric properties; Allosteric Regulation; Allosteric Site; Alzheimer's disease; Analysis; Animals; Aspartic proteases; ATP; Automation; Binding sites; Biochemistry; Biology; Biophysics; Chromatography; Crystal structure; Crystallography, X-Ray; Datasets; Diabetes; Electron density; Enzymatic activity; Enzyme activity; Enzymes; Insulin; Insulysin; Insulysin - chemistry; Insulysin - metabolism; Kinetics; Life sciences; Ligands; Mass Spectrometry; Metabolism; Models, Molecular; Mutant Proteins - chemistry; Mutant Proteins - metabolism; Mutation - genetics; Neurodegenerative diseases; Peptides; Physiological aspects; Polyphosphates; Protein Binding; Protein Multimerization; Protein Structure, Secondary; Proteins; Proteolysis; Proteolytic enzymes; Rats; Reaction kinetics; Scientific imaging; Spectrometry, Fluorescence; Type 2 diabetes
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0020864

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. 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. 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.