TY - JOUR
T1 - Magnetic circular dichroism used to examine the interaction of Escherichia coli cytochrome bd with ligands
AU - Borisov, Vitaliy
AU - Arutyunyan, Alexander M.
AU - Osborne, Jeffrey P.
AU - Gennis, Robert B.
AU - Konstantinov, Alexander A.
PY - 1999/1/12
Y1 - 1999/1/12
N2 - The interactions of the fully reduced and fully oxidized cytochrome bd from E. coli with ligands CO, NO, and CN- have been studied by a combination of absorption and magnetic circular dichroism (MCD) spectroscopy. In the reduced cytochrome bd, MCD resolves individual bands due to the high-spin heme b595 and the low-spin heme b558 components of the enzyme, allowing one to separately monitor their interactions along with ligand binding to the heme d component. The data show that at low concentrations, the ligands bind almost exclusively to heme d. At high concentrations, the ligands begin to interact with the low-spin heme b558. At the same time, no evidence for significant binding of the ligands to the high-spin heme b595 is revealed in either the reduced or the fully oxidized cytochrome bd complex. The data support the model [Borisov, V. B., Gennis, R. B., and Konstantinov, A. A. (1995) Biochemistry (Moscow) 60, 231-239] according to which the two high- spin hemes d and b595 share a high-affinity ligand binding site with a capacity for only a single molecule of the ligand; i.e., there is a strong negative cooperativity with respect to ligand binding to these two hemes with cytochrome d having: an intrinsic ligand affinity much higher than that of heme b595.
AB - The interactions of the fully reduced and fully oxidized cytochrome bd from E. coli with ligands CO, NO, and CN- have been studied by a combination of absorption and magnetic circular dichroism (MCD) spectroscopy. In the reduced cytochrome bd, MCD resolves individual bands due to the high-spin heme b595 and the low-spin heme b558 components of the enzyme, allowing one to separately monitor their interactions along with ligand binding to the heme d component. The data show that at low concentrations, the ligands bind almost exclusively to heme d. At high concentrations, the ligands begin to interact with the low-spin heme b558. At the same time, no evidence for significant binding of the ligands to the high-spin heme b595 is revealed in either the reduced or the fully oxidized cytochrome bd complex. The data support the model [Borisov, V. B., Gennis, R. B., and Konstantinov, A. A. (1995) Biochemistry (Moscow) 60, 231-239] according to which the two high- spin hemes d and b595 share a high-affinity ligand binding site with a capacity for only a single molecule of the ligand; i.e., there is a strong negative cooperativity with respect to ligand binding to these two hemes with cytochrome d having: an intrinsic ligand affinity much higher than that of heme b595.
UR - http://www.scopus.com/inward/record.url?scp=0033547815&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033547815&partnerID=8YFLogxK
U2 - 10.1021/bi981908t
DO - 10.1021/bi981908t
M3 - Article
C2 - 9888814
AN - SCOPUS:0033547815
SN - 0006-2960
VL - 38
SP - 740
EP - 750
JO - Biochemistry
JF - Biochemistry
IS - 2
ER -