Premium
Fourier‐transform infrared studies on azide‐binding to the binuclear center of the Escherichia coli bo ‐type ubiquinol oxidase 1
Author(s) -
Tsubaki Motonari,
Mogi Tatsushi,
Hori Hiroshi
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00423-8
Subject(s) - azide , chemistry , fourier transform infrared spectroscopy , infrared spectroscopy , crystallography , photochemistry , infrared , oxidase test , stereochemistry , enzyme , organic chemistry , physics , quantum mechanics , optics
Azide‐binding to the heme‐copper binuclear center of bo ‐type ubiquinol oxidase from Escherichia coli was investigated with Fourier‐transform infrared spectroscopy. Deconvolution analyses of infrared spectra of the azide ( 14 N 3 )‐inhibited air‐oxidized form showed a major infrared azide antisymmetric stretching band at 2041 cm −1 . An additional band developed at 2062.5 cm −1 during a longer incubation. Isotope substitutions with terminally 15 N‐labelled azides did not show a splitting of the major band, indicating that the geometry of the bound azide is mainly in a bridging configuration between high‐spin heme o and Cu B . The band at 2062.5 cm −1 showed clear splittings upon substitution with the terminally 15 N‐labelled azides, indicating the Cu B 2+ ‐N=N=N structure. Partial reduction of the oxidase with β‐NADH in the presence of azide caused an appearance of new infrared bands at 2038.5 (major) and 2009 (minor) cm −1 . The former band also showed clear splittings in the presence of the terminally 15 N‐labelled azides, indicating that reduction of low‐spin heme b alters the structure of the binuclear center leading to the Fe o 3+ ‐N=N=N configuration.