Rapid cross-linking of proteins by 4-ketoaldehydes and 4-hydroxy-2-alkenals does not arise from the lysine-derived monoalkylpyrroles.
Exposure of proteins to 4-hydroxy-2-nonenal (HNE) results in conversion of lysines in part to 2-pentylpyrroles that can be formed in higher yield by exposure to the isomeric 4-oxononanal. Since both HNE and 4-oxononanal cause protein cross-linking, and since pyrrolation of proteins by gamma-diketones is also known to result in protein cross-linking, it has been considered that the initially formed 2-pentylpyrroles are responsible for the protein cross-linking seen for HNE and 4-oxononanal. Here we show that protein-bound 2-alkylpyrrole products associated with modification by 4-hydroxy-2-alkenals and 4-oxoalkanals, possessing only monoalkyl substitution, induce undetectable levels of autoxidation-mediated protein cross-linking over time periods where the parent aldehydes effect extensive protein cross-linking, which then must be occurring through alternative mechanisms. Finally, using both RNase and BSA, our finding that reductive methylation of lysines blocks protein cross-linking induced by either HNE or 4-oxononanal (and development of fluorescence in the case of HNE) implicates the obligatory role of lysines in the cross-linking reactions.
Xu
G
G
Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Liu
Y
Y
Kansal
M M
MM
Sayre
L M
LM
D000447:Aldehydes / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D003432:Cross-Linking Reagents / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D006588:Hexanones / Q000737:chemistry; D008239:Lysine / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*; D012259:Ribonuclease, Pancreatic / Q000737:chemistry; D012545:Schiff Bases / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry
D000447:Aldehydes; D003432:Cross-Linking Reagents; D006588:Hexanones; D011506:Proteins; D011758:Pyrroles; D012545:Schiff Bases; D012710:Serum Albumin, Bovine; C011269:2,5-hexanedione; D012259:Ribonuclease, Pancreatic; C027576:4-hydroxy-2-nonenal; D008239:Lysine