ISSN:
1573-6881
Keywords:
Cytochromec oxidase
;
infrared
;
carbon monoxide
;
cyanide
;
azide
;
secondary structure
;
anesthetics
;
nitrous oxide
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Physics
Notes:
Abstract IR spectra directly probe specific vibrators in bovine heart cytochromec oxidase, yielding quantitative as well as qualitative information on structures and reactions at these vibrators. C-O IR spectra reveal that CO binds to $$Fe_{a_3 }^{2 + } $$ as two conformers each in isolated immobile environments sensitive to Fe a and/or CuA oxidation state but remarkably insensitive to pH, medium, anesthetics, and other factors that affect activity. C-N IR spectra reveal that the one CN− that binds to fully and partially oxidized enzyme can be in three different structures. These structures vary in relative amounts with redox level, thereby reflecting dynamic electron exchange among Fe a , CuA, and CuB with associated changes in protein conformation of likely significance in O2 reduction and H+-pumping. Azide IR spectra also reflect redox-dependent long-range effects. The amide I IR bands, due to C-O vibrators of peptide linkages and composed of multiple bands derived from different secondary structures, reveal high levels of α-helix (∼60%) and subtle changes with redox level and exposure to anesthetics. N2O IR spectra reveal that these anesthetic molecules at clinically relevant levels occupy three sites of different polarity within the enzyme as the enzyme is reversibly, but only partially, inhibited.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00762850
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