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Abstract

Nickel is harmful to humans, being both carcinogenic and allergenic. However, the mechanisms of this toxicity are still unresolved. We propose that Ni(II) ions disintegrate proteins by hydrolysis of peptide bonds preceding the Ser/Thr−Xaa−His sequences. Such sequences occur in nuclear localization signals (NLSs) of human phospholipid scramblase 1, Sam68‐like mammalian protein 2, and CLK3 kinase. We performed spectroscopic experiments showing that model nonapeptides derived from these NLSs bind Ni(II) at physiological pH. We also proved that these sequences are prone to Ni(II) hydrolysis. Thus, the aforementioned NLSs may be targets for nickel toxicity. This implies that Ni(II) ions disrupt the transport of some proteins from cytoplasm to cell nucleus.
Chem. Biodiversity 2020; 17: e1900652
Peptide bond cleavage by Ni(II) ions within the nuclear
localization signal sequence
Tomasz Frączyk,* Arkadiusz Bonna, Ewelina Stefaniak, Nina E.
Wezynfeld, Wojciech Bal
tfraczyk@ibb.waw.pl
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... The Ser/Thr-Xaa-His sequence occurs in several human proteins. We have shown that histone H2A [18], annexins A1, A2, and A8 [19], alpha-1-antitrypsin [20], phospholipid scramblase 1, Sam68-like mammalian protein 2, and CLK3 kinase [21] contain surface-exposed fragments cleavable by Ni(II) ions. Ni(II)-prone sequences are also present in all of the melatonin biosynthesis pathway enzymes, i.e., tryptophan 5-hydroxylase 1 (TPH1), aromatic-L-amino-acid decarboxylase (AADC), serotonin N-acetyltransferase (SNAT), and acetylserotonin O-methyltransferase (ASMT). ...
... The Ser/Thr-Xaa-His sequence occurs in several human proteins. We have shown that histone H2A [18], annexins A1, A2, and A8 [19], alpha-1-antitrypsin [20], phospholipid scramblase 1, Sam68-like mammalian protein 2, and CLK3 kinase [21] contain surfaceexposed fragments cleavable by Ni(II) ions. Ni(II)-prone sequences are also present in all of the melatonin biosynthesis pathway enzymes, i.e., tryptophan 5-hydroxylase 1 (TPH1), aromatic-L-amino-acid decarboxylase (AADC), serotonin N-acetyltransferase (SNAT), and acetylserotonin O-methyltransferase (ASMT). ...
... We chose physiological temperature (37 • C) and two pH values, 7.4 and 8.2, close to those existing in cytoplasm and mitochondria, respectively. Such pH values were also used in our previous publications [17,[19][20][21]39]. Thus, it is also possible to compare the measured hydrolysis rates with other peptides. ...
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