NMR analysis of synthetic human serum albumin alpha-helix 28 identifies structural distortion upon amadori modification.
The non-enzymatic reaction between reducing sugars and long-lived proteins in vivo results in the formation of glycation and advanced glycation end products, which alter the properties of proteins including charge, helicity, and their tendency to aggregate. Such protein modifications are linked with various pathologies associated with the general aging process such as Alzheimer disease and the long-term complications of diabetes. Although it has been suggested that glycation and advanced glycation end products altered protein structure and helicity, little structural data and information currently exist on whether or not glycation does indeed influence or change local protein secondary structure. We have addressed this problem using a model helical peptide system containing a di-lysine motif derived from human serum albumin. We have shown that, in the presence of 50 mm glucose and at 37 degrees C, one of the lysine residues in the di-lysine motif within this peptide is preferentially glycated. Using NMR analysis, we have confirmed that the synthetic peptide constituting this helix does indeed form a alpha-helix in solution in the presence of 30% trifluoroethanol. Glycation of the model peptide resulted in the distortion of the alpha-helix, forcing the region of the helix around the site of glycation to adopt a 3(10) helical structure. This is the first reported evidence that glycation can influence or change local protein secondary structure. The implications and biological significance of such structural changes on protein function are discussed.
Howard
Mark J
MJ
Protein Science Group, Department of Biosciences, University of Kent, Canterbury, UK.
Smales
C Mark
CM
D020816:Amino Acid Motifs; D005947:Glucose / Q000494:pharmacology; D017127:Glycation End Products, Advanced; D006031:Glycosylation; D006801:Humans; D006860:Hydrogen Bonding; D008239:Lysine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D015202:Protein Engineering / Q000379:methods; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012709:Serum Albumin / Q000737:chemistry*; D013696:Temperature; D014270:Trifluoroethanol / Q000494:pharmacology
D017127:Glycation End Products, Advanced; D010455:Peptides; D012709:Serum Albumin; D014270:Trifluoroethanol; D005947:Glucose; D008239:Lysine