Substrate binding activates the designed triple mutant of the colicin E7 metallonuclease

Eszter Németh, Tamás Körtvélyesi, Milan Kožíšek, Peter Waaben Thulstrup, Hans Erik Mølager Christensen, Masamitsu N. Asaka, Kyosuke Nagata, Béla Gyurcsik*

*Corresponding author af dette arbejde
6 Citationer (Scopus)

Abstract

The nuclease domain of colicin E7 (NColE7) cleaves DNA nonspecifically. The active center is a Zn2+-containing HNH motif at the C-terminus. The N-terminal loop is essential for the catalytic activity providing opportunity for allosteric modulation of the enzyme. To identify the key residues responsible for the structural integrity of NColE7, a virtual alanine scan was performed on a semiempirical quantum chemical level within the 25 residue long N-terminal sequence (446-470). Based on the calculations the T454A/K458A/W464A-NColE7 triple mutant (TKW) was expressed and purified. According to the agarose gel electrophoresis experiments and linear dichroism spectra the catalytic activity of the TKW mutant decreased in comparison with wild-type NColE7. The distorted structure and weakened Zn2+ binding may account for this as revealed by circular dichroism spectra, mass spectrometry, fluorescence-based thermal analysis and isothermal microcalorimetric titrations. Remarkably, the substrate induced the folding of the mutant protein.

OriginalsprogEngelsk
TidsskriftJournal of Biological Inorganic Chemistry
Vol/bind19
Udgave nummer8
Sider (fra-til)1295-1303
Antal sider9
ISSN0949-8257
DOI
StatusUdgivet - 2014

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