TY - JOUR
T1 - Solution structure of proinsulin
T2 - Connecting domain flexibility and prohormone processing
AU - Yang, Yanwu
AU - Hua, Qing Xin
AU - Liu, Jin
AU - Shimizu, Eri H.
AU - Choquette, Meredith H.
AU - Mackin, Robert B.
AU - Weiss, Michael A.
PY - 2010/3/12
Y1 - 2010/3/12
N2 - The folding of proinsulin, the single-chain precursor of insulin, ensures native disulfide pairing in pancreatic β-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 {1H}-15N nuclear Overhauser enhancements) is progressively less ordered. Although the BC junction is flexible, residues near the CA junction exhibit α-helical-like features. Relative to canonical α-helices, however, segmental 13Cα/β 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.
AB - The folding of proinsulin, the single-chain precursor of insulin, ensures native disulfide pairing in pancreatic β-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 {1H}-15N nuclear Overhauser enhancements) is progressively less ordered. Although the BC junction is flexible, residues near the CA junction exhibit α-helical-like features. Relative to canonical α-helices, however, segmental 13Cα/β 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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U2 - 10.1074/jbc.C109.084921
DO - 10.1074/jbc.C109.084921
M3 - Article
C2 - 20106974
AN - SCOPUS:77950915587
SN - 0021-9258
VL - 285
SP - 7847
EP - 7851
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 11
ER -