Cross‐linking of a synthetic partial‐length (1–28) peptide of the Alzheimer β/A4 amyloid protein by transglutaminase

Abstract

Cerebral deposits of iliA4 amyloid protein is a pathologic sign of Alzheimer's disease. A synthetic partial-length (I 28) peptide of this protein contains one glutamine and two lysine residues. Here we show that this peptide can be a substrate oftransglutaminase, which catalyzes cross-linking between glutamine and lysine residues in peptides, by demonstrating the formation of multimeric peptides due to the action of this enzyme. A modified (Lys 2s to L-norleucine) version of the synthetic peptide was also cross-linked, but another modified version (Lys ~6 to L-norleucine) was very poorly cross-linked, indicating that Lys 16 is involved exclusively in the cross-linking of the partial-length peptide catalyzed by transglutaminase.Transglutaminase; Amyloid beta-protein; Alzheimer's disease.

Identification of glutamine and lysine residues in Alzheimer amyloid βA4 peptide responsible for transglutaminase‐catalysed homopolymerization and cross‐linking to α2M receptor

“…The present results are in general agreement with the recent finding that a partial-length (l-28) /?A4 peptide is a substrate for TG [26]. Whether Lys16 and/or Lys" participate in the cross-linking of /?A4 remains to be elucidated.…”

“…Whether Lys16 and/or Lys" participate in the cross-linking of /?A4 remains to be elucidated. By using two modified versions of the partiallength /?A4 peptide (Lys16 or Lys2' replaced by L-norleutine) Ikura et al [26] found that Lys16 was involved exclusively in the polymerization. However, exclusion of Lys2* as a potential donor site is questionable, since this amino acid is positioned C-terminal in the partial-length peptide.…”

“…While this work was in progress, Ikura et al [26] reported that a partial-length (l-28) /?A4 peptide formed homopolymers in the presence of TG. In this report, we show that /?A4 in a TG-catalysed reaction is able to homopolymerize and to form heteropolymers with extracellular matrix proteins as well as a,M receptor, a recently discovered protein in neurons [16] and in AD plaques [17].…”

Propagating structure of Alzheimer’s β-amyloid (10–35) is parallel β-sheet with residues in exact register

“…This enzyme specifically crosslinks Gln 15 and Lys 16 of A␤ but never involves Lys 28 (70), suggesting that Gln 15 and Lys 16 are proximate in an aggregated form of A␤. For our experiments, we synthesized a 26-aa peptide, comprising residues 10-35 of the A␤ peptide (A␤ (10-35) , Fig.…”

“…The decision of where to place these labels was aided by studies of tissue transglutaminase (tTg) crosslinking of A␤ (66)(67)(68)(69)(70). This enzyme specifically crosslinks Gln 15 and Lys 16 of A␤ but never involves Lys 28 (70), suggesting that Gln 15 and Lys 16 are proximate in an aggregated form of A␤.…”