A detailed resonance Raman spectrum of Nickel(II)-substituted Pseudomonas aeruginosa azurin.
Nickel(II) and cobalt(II) derivatives of the blue copper protein Pseudomonas aeruginosa azurin have been studied by resonance Raman (RR) spectroscopy at liquid-nitrogen temperatures. Vibrational assignments for the observed RR bands of Ni(II)-azurin have been made through a study of (62)Ni-substituted azurin. A comparison of Ni(II)-azurin RR spectra with those of the wild type (Cu-containing) protein showed Ni(II)-S(Cys) stretching vibrations, nu(Ni-S)(Cys), at substantially lower frequencies (approximately 360 versus approximately 400 cm(-1), respectively), indicating that the Ni(II)-S(Cys) bond is much weaker than the corresponding Cu(II)-S(Cys) bond. Resonance enhanced predominantly nu(Ni-N)(His) modes indicate that the metal-N(His) bond distances in the Ni(II) derivative are the same as those in native azurin. The vibrational data also confirm a tetrahedral disposition of ligands about the metal in Ni(II)-azurin found in the protein crystallographic structures. As expected, excitation profile measurements on Ni(II)-azurin show that the nu(Ni-S)(Cys) assignable modes give maxima at the 440-nm absorption band, which confirms a S(Cys) --> Ni(II) charge-transfer origin of the 440-nm electronic transition in Ni(II)-substituted azurin.
Czernuszewicz
Roman S
RS
Department of Chemistry, University of Houston, Texas 77204-5003, USA. Roman@uh.edu
Fraczkiewicz
Grazyna
G
Zareba
Adelajda A
AA
D001400:Azurin / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D003300:Copper / Q000737:chemistry; D004563:Electrochemistry; D008667:Metalloproteins / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry*; D011550:Pseudomonas aeruginosa / Q000737:chemistry*; D013059:Spectrum Analysis, Raman
D008667:Metalloproteins; D001400:Azurin; D003035:Cobalt; D003300:Copper; D009532:Nickel