Stable intrachain and interchain complexes of neurofilament peptides: A putative link between Al3+ and Alzheimer disease

M. Hollosi, Min Shen Zhi Min Shen, A. Perczel, G. D. Fasman

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Abstract

The etiologic role of Al3+ in Alzheimer disease has been controversial. Circular dichroism (CD) spectroscopic studies on two synthetic fragments of human neurofilament protein mid-sized subunit (NF-M), NF-M13 (KSPVPKSPVEEKG) and NF-M17 (EEKGKSPVPKSPVEEKG), and their alanine-substituted and/or serine- phosphorylated derivatives were carried out in an attempt to find a molecular mechanism for the effect of Al3+ to induce aggregation of neuronal proteins or their catabolic fragments. Al3+ and Ca2+ ions were found to induce β- pleated sheet formation in the phosphorylated fragments. The cation sensitivity depended on the length and charge distribution of the sequence and site of phosphorylation. Al3+-induced conformational changes were irreversible to citric acid chelation, whereas Ca2+-induced conformational changes were reversible with citric acid. Studies of the alanine derivatives demonstrated which residues affected Al3+ or Ca2+ binding. Peptides containing at least one free (nonphosphorylated) serine residue were shown to form an intramolecular Al3+ complex, rather than an intermolecular one. In the intramolecular (intrachain) complex, the ligand function of the deprotonated serine hydroxyl was delineated [(Al·pepH-1)-type complex]. Ca2+ ions did not show a tendency for intramolecular complexing. The potential role of Al3+ in Alzheimer disease tangle and plaque formation is strongly suggested.

Original languageEnglish
Pages (from-to)4902-4906
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume91
Issue number11
DOIs
Publication statusPublished - Jun 7 1994

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Keywords

  • circular dichroism
  • conformational changes
  • phosphorylated derivatives

ASJC Scopus subject areas

  • General

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