2KQP | pdb_00002kqp

Solution structure of proinsulin: connecting domain flexibility and prohormone processing.

(2010) J Biological Chem 285: 7847-7851

• PubMed: 20106974 Search on PubMedSearch on PubMed Central
• DOI: https://doi.org/10.1074/jbc.C109.084921
• Primary Citation of Related Structures:  
  2KQP


• PubMed Abstract: 
  

  The folding of proinsulin, the single-chain precursor of insulin, ensures native disulfide pairing in pancreatic beta-cells. Mutations that impair folding cause neonatal diabetes mellitus. Although the classical structure of insulin is well established, proinsulin is refractory to crystallization. Here, we employ heteronuclear NMR spectroscopy to characterize a monomeric analogue. Proinsulin contains a native-like insulin moiety (A- and B-domains); the tethered connecting (C) domain (as probed by {(1)H}-(15)N nuclear Overhauser enhancements) is progressively less ordered. Although the BC junction is flexible, residues near the CA junction exhibit alpha-helical-like features. Relative to canonical alpha-helices, however, segmental (13)C(alpha/beta) chemical shifts are attenuated, suggesting that this junction and contiguous A-chain residues are molten. We propose that flexibility at each C-domain junction facilitates prohormone processing. Studies of protease SPC3 (PC1/3) suggest that C-domain sequences contribute to cleavage site selection. The structure of proinsulin provides a foundation for studies of insulin biosynthesis and its impairment in monogenic forms of diabetes mellitus.

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Organizational Affiliation: 

Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA. yanwu.yang@case.edu