tailieunhanh - Báo cáo khoa học: Solution structure of human proinsulin C-peptide

The C-peptide of proinsulin is important for the biosynthesis of insulin, but has been considered for a long time to be biologically inert. Recent studies in diabetic patients have stimulated a new debate about its possible regulatory role, suggesting that it is a hormonally active peptide. We des-cribe structural studies of the C-peptide using 2D NMR spectroscopy. | iFEBS Journal Solution structure of human proinsulin C-peptide Claudia Elisabeth Munte1 Luciano Vilela2 Hans Robert Kalbitzer3 and Richard Charles Garratt1 1 Institute de Fisica de Sao Carlos Universidade de Sao Paulo Sao Carlos Brazil 2 Biomm . Montes Claros Brazil 3 Institut fur Biophysik und Physikalische Biochemie Universitat Regensburg Germany Keywords CA knuckle NMR proinsulin C-peptide protein secondary structure Correspondence H. R. Kalbitzer Institut fur Biophysik und Physikalische Biochemie Universitat Regensburg 93040 Regensburg Germany Tel 49 94l 943 2595 E-mail . R. C. Garratt Instituto de Fisica de Sao Carlos Universidade de Scio Paulo Caixa Postal369 13560-970 Sao Carlos SP Brazil Tel 55 16 33739881 Fax 55 16 33739881 E-mail richard@ Received 9 March 2005 revised 25 May 2005 accepted 4 July 2005 The C-peptide of proinsulin is important for the biosynthesis of insulin but has been considered for a long time to be biologically inert. Recent studies in diabetic patients have stimulated a new debate about its possible regulatory role suggesting that it is a hormonally active peptide. We describe structural studies of the C-peptide using 2D NMR spectroscopy. In aqueous solution the NOE patterns and chemical shifts indicate that the ensemble is a nonrandom structure and contains substructures with defined local conformations. These are more clearly visible in 50 H2O 50 2 2 2-trifluoroethanol. The N-terminal region residues 2-5 forms a type I b-turn whereas the C-terminal region residues 27-31 presents the most well-defined structure of the whole molecule including a type III b-turn. The C-terminal pentapeptide EGSLQ has been suggested to be responsible for chiral interactions with an as yet uncharacterized probably a G-protein-coupled receptor. The three central regions of the molecule residues 9-12 15-18 and 22-25 show tendencies to form b-bends. We propose that the structure described here .