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Related Experiment Videos

Predicted structural alterations in proinsulin during its interactions with prohormone convertases

G Lipkind1, D F Steiner

  • 1Department of Biochemistry and Molecular Biology, The Howard Hughes Medical Institute, The University of Chicago, Illinois 60637, USA.

Biochemistry
|January 20, 1999
PubMed
Summary

Proinsulin processing involves cleavage at specific sites by convertases. This study proposes a conformational model of proinsulin that facilitates enzyme-substrate interactions for efficient insulin production.

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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Proinsulin is intracellularly converted to insulin through cleavage at two specific dibasic sites.
  • This conversion is catalyzed by subtilisin-like prohormone convertases, SPC3 (PC1/PC3) and SPC2 (PC2).

Purpose of the Study:

  • To propose a conformational variant of proinsulin that facilitates enzyme-substrate complex formation.
  • To model the interactions between proinsulin processing sites and convertase enzymes.

Main Methods:

  • Computational modeling of proinsulin conformation.
  • Analysis of enzyme-substrate interactions at processing junctions.
  • Stereochemical modeling of proinsulin processing by SPC2.

Main Results:

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  • A model of a reactive proinsulin conformation is presented where processing sites are spatially separated.
  • Extended peptide conformations at CA and BC junctions are required for productive convertase interaction.
  • The C-peptide adopts an extended loop conformation in the modeled reactive state.

Conclusions:

  • The proposed conformational variant of proinsulin explains efficient processing by SPC2 and SPC3.
  • Understanding proinsulin conformation is key to elucidating insulin biosynthesis.
  • This model provides insights into the stereochemical basis of prohormone processing.