ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
SL24. Nickel-related Peptide Bond Hydrolysis: from Carcinogenesis to
Biotechnology
W. Bal a , E. Kopera a , A. Krężel b , J. Poznański a , A. Wysłouch-Cieszyńska a
a
Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106, Warsaw,
Poland,
b
Faculty of Biotechnology, University of Wrocław, Tamka 2, 50-137, Wrocław, Poland
e-mail: wbal@ibb.waw.pl
Ni(II) is a human carcinogen, with molecular targets in the cell nucleus. A search of Ni(II) binding sites in
histones – main nuclear proteins – yielded a sequence-specific Ni(II)-dependent reaction of peptide bond
hydrolysis in model peptides and histone H2A: extTE!SHHKext (! = cleavage site, ext = chain extension). The
reaction was stoichiometric, with Ni(II) bound as a square-planar (sp) complex with the C-terminal reaction
product. This links the epigenetic and oxidative concepts in nickel carcinogenesis, as sp Ni(II) peptidic
complexes are known oxidants [1]. Further studies revealed that the cleavage occurs in nearly all ext!BXHZext
sequences (B = S or T), upon the formation of a specific “4N” sp complex involving the Ni(II) ion bound to B,
X, and H residues [2]. The reaction starts with the acyl shift from the B amide to its OH group, followed by
hydrolysis of the resulting ester. The B residue nitrogen remains bonded to Ni(II). Its amide-to-amine conversion
promotes the reaction by enhancing Ni(II) binding. The reaction can be made highly sequence-specific at lower
pH ~8. Bulky and hydrophobic X and Z residues are preferred (e.g. !SRHW), as shown by a combinatorial
library. The presence of all required residues (!BXHZ) in the C-terminal product suggested an application of the
reaction for removing affinity tags from recombinant proteins. A successful demonstration of such process
completed a pathway of our discovery from basic research to practical applications.
References:
[1] AA Karaczyn, W Bal, SL North, RM Bare, VM Hoang, RJ Fisher, KS Kasprzak, The octapeptidic end of the
C-terminal tail of histone H2A is cleaved-off in cells exposed to carcinogenic Ni(II). Chem Res Toxicol 16,
1555-1559, 2003 and refs. therein.
[2] A Krężel, M Mylonas, E Kopera, W Bal, Sequence-specific Ni(II)-dependent peptide bond hydrolysis in a
peptide containing threonine and histidine residues, Acta Biochim Polon 53, 721–727, 2006
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