biostudies-literatureJi MNCRR NIH HHSNIGMS NIH HHS3173-3182https://www.ebi.ac.uk/biostudies/studies/S-EPMC4350447biostudies-literatureUnknown112(24)The EcoRI restriction endonuclease requires one divalent metal ion in each of two symmetrical and identical catalytic sites to catalyse double-strand DNA cleavage. Recently, we showed that Cu²⁺ binds outside the catalytic sites to a pair of new sites at H114 in each sub-unit, and inhibits Mg²⁺ -catalysed DNA cleavage. In order to provide more detailed structural information on this new metal ion binding site, we performed W-band (~94 GHz) and X-band (~9.5 GHz) electron spin resonance spectroscopic measurements on the EcoRI-DNA-(Cu²⁺ )₂ complex. Cu²⁺ binding results in two distinct components with different <i>g</i>_zz and <i>A</i>_zz values. X-band electron spin echo envelope modulation results indicate that both components arise from a Cu²⁺ coordinated to histidine. This observation is further confirmed by the hyperfine sub-level correlation results. W-band electron nuclear double resonance spectra provide evidence for equatorial coordination of water molecules to the Cu²⁺ ions.Molecular physicsInsights into copper coordination in the EcoRI-DNA complex by ESR spectroscopy.PMC4350447R37 GM029207S10 RR028701R01 GM029207Tan LJen-Jacobson LSaxena SJi MfalseInsights into copper coordination in the EcoRI-DNA complex by ESR spectroscopy.The EcoRI restriction endonuclease requires one divalent metal ion in each of two symmetrical and identical catalytic sites to catalyse double-strand DNA cleavage. Recently, we showed that Cu²⁺ binds outside the catalytic sites to a pair of new sites at H114 in each sub-unit, and inhibits Mg²⁺ -catalysed DNA cleavage. In order to provide more detailed structural information on this new metal ion binding site, we performed W-band (~94 GHz) and X-band (~9.5 GHz) electron spin resonance spectroscopic measurements on the EcoRI-DNA-(Cu²⁺ )₂ complex. Cu²⁺ binding results in two distinct components with different <i>g</i>_zz and <i>A</i>_zz values. X-band electron spin echo envelope modulation results indicate that both components arise from a Cu²⁺ coordinated to histidine. This observation is further confirmed by the hyperfine sub-level correlation results. W-band electron nuclear double resonance spectra provide evidence for equatorial coordination of water molecules to the Cu²⁺ ions.2014-01-01T00:00:00Z2014 Dec2024-10-14T22:30:47.917Z2019-03-27T01:47:37ZS-EPMC43504472575046110.1080/00268976.2014.934313