Macromolecule Content

• Total Structure Weight: 5.72 kDa 
• Atom Count: 397 
• Residue Count: 51 
• Unique protein chains: 2

2K91

Enhancing the activity of insulin by stereospecific unfolding

• DOI: 10.2210/pdb2K91/pdb
• BMRB: 16027

• Classification: HORMONE
• Organism(s): Homo sapiens
• Expression System: Escherichia coli
• Mutation(s): Yes 


• Deposited: 2008-09-29 Released: 2008-11-18 
• Deposition Author(s): Hua, Q.X., Xu, B., Huang, K., Hu, S.Q., Nakarawa, S., Jia, W.H., Philips, N.F.P., Wittaker, L., Wittaker, J., Katsoyannis, P.G., Weiss, M.A.

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Experimental Data Snapshot

• Method: SOLUTION NMR
• Conformers Calculated: 40 
• Conformers Submitted: 20 
• Selection Criteria: structures with the lowest energy 

Literature

Enhancing the Activity of a Protein by Stereospecific Unfolding: CONFORMATIONAL LIFE CYCLE OF INSULIN AND ITS EVOLUTIONARY ORIGINS.

Hua, Q.X., Xu, B., Huang, K., Hu, S.Q., Nakagawa, S., Jia, W., Wang, S., Whittaker, J., Katsoyannis, P.G., Weiss, M.A.

(2009) J Biol Chem 284: 14586-14596

• PubMed: 19321436 
• DOI: 10.1074/jbc.M900085200
• Primary Citation of Related Structures:  
  2K91, 2K9R


• PubMed Abstract: 
  

A central tenet of molecular biology holds that the function of a protein is mediated by its structure. An inactive ground-state conformation may nonetheless be enjoined by the interplay of competing biological constraints. A model is provided by insulin, well characterized at atomic resolution by x-ray crystallography. Here, we demonstrate that the activity of the hormone is enhanced by stereospecific unfolding of a conserved structural element. A bifunctional beta-strand mediates both self-assembly (within beta-cell storage vesicles) and receptor binding (in the bloodstream). This strand is anchored by an invariant side chain (Phe(B24)); its substitution by Ala leads to an unstable but native-like analog of low activity. Substitution by d-Ala is equally destabilizing, and yet the protein diastereomer exhibits enhanced activity with segmental unfolding of the beta-strand. Corresponding photoactivable derivatives (containing l- or d-para-azido-Phe) cross-link to the insulin receptor with higher d-specific efficiency. Aberrant exposure of hydrophobic surfaces in the analogs is associated with accelerated fibrillation, a form of aggregation-coupled misfolding associated with cellular toxicity. Conservation of Phe(B24), enforced by its dual role in native self-assembly and induced fit, thus highlights the implicit role of misfolding as an evolutionary constraint. Whereas classical crystal structures of insulin depict its storage form, signaling requires engagement of a detachable arm at an extended receptor interface. Because this active conformation resembles an amyloidogenic intermediate, we envisage that induced fit and self-assembly represent complementary molecular adaptations to potential proteotoxicity. The cryptic threat of misfolding poses a universal constraint in the evolution of polypeptide sequences.

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Organizational Affiliation: 

Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Insulin	A	21	Homo sapiens	Mutation(s): 0  Gene Names: INS
Find proteins for P01308 (Homo sapiens) Explore P01308  Go to UniProtKB:  P01308
NIH Common Fund Data Resources
PHAROS  P01308

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
Insulin	B	30	Homo sapiens	Mutation(s): 4  Gene Names: INS
Find proteins for P01308 (Homo sapiens) Explore P01308  Go to UniProtKB:  P01308
NIH Common Fund Data Resources
PHAROS  P01308

Experimental Data & Validation

Experimental Data

• Method: SOLUTION NMR
• Conformers Calculated: 40 
• Conformers Submitted: 20 
• Selection Criteria: structures with the lowest energy 
• OLDERADO: 2K91 Olderado

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2008-09-29 
• Released Date: 2008-11-18 
Deposition Author(s): Hua, Q.X., Xu, B., Huang, K., Hu, S.Q., Nakarawa, S., Jia, W.H., Philips, N.F.P., Wittaker, L., Wittaker, J., Katsoyannis, P.G., Weiss, M.A.

Revision History 

• Version 1.0: 2008-11-18
  Type: Initial release
  
• Version 1.1: 2011-07-13
  Changes: Version format compliance