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The formation and structure of proinsulin C-peptide oligomers has been investigated by PAGE, NMR spectroscopy and dynamic light scattering. The results obtained show that C-peptide forms oligomers of different sizes, and that their formation and size distribution is altered by salt and divalent metal ions, which indicates that the aggregation process is medi-ated by electrostatic interactions. | ỊFEBS Journal Structural features of proinsulin C-peptide oligomeric and amyloid states I I I 1 I I I I I 2. A I I KU __1_ A III I I 2 I I I I 2 I Jesper Lind Emma Lindahl Alex Peralvarez-Marin Anna Holmlund Hans Jornvall and Lena Maler1 1 Department of Biochemistry and Biophysics Center for Biomembrane Research The Arrhenius laboratory Stockholm University Sweden 2 Department of MedicalBiochemistry and Biophysics Karolinska Institutet Stockholm Sweden Keywords C-peptide diabetes oligomer spectroscopy structure Correspondence L. Maler Department of Biochemistry and Biophysics Center for Biomembrane Research The Arrhenius laboratory Stockholm University SE-106 91 Stockholm Sweden Fax 46 8 155597 Tel 46 8 162448 E-mail lena.maler@dbb.su.se Present Address Department of Molecular and Cell Biology Harvard University Cambridge MA 02138 USA These authors contributed equally to this work Received 27 May 2010 revised 8 July 2010 accepted 13 July 2010 doi 10.1111 j.1742-4658.2010.07777.x The formation and structure of proinsulin C-peptide oligomers has been investigated by PAGE NMR spectroscopy and dynamic light scattering. The results obtained show that C-peptide forms oligomers of different sizes and that their formation and size distribution is altered by salt and divalent metal ions which indicates that the aggregation process is mediated by electrostatic interactions. It is further demonstrated that the size distribution of the C-peptide oligomers in agreement with previous studies is altered by insulin which supports a physiologically relevant interaction between these two peptides. A small fraction of oligomers has previously been suggested to be in equilibrium with a dominant fraction of soluble monomers and this pattern also is observed in the present study. The addition of modest amounts of sodium dodecyl sulphate at low pH increases the relative amount of oligomers and this effect was used to investigate the details of both oligomer formation and structure by a .
