The kinetics of ligand binding to plant hemoglobins. Structural implications.
The rates of reaction of oxygen, carbon monoxide, and nitric oxide with 14 plant hemoglobins have been determined by relaxation and stopped-flow methods. The combination rates for oxygen lie between 0.12 and 0.26 x 10(9)/M.s, for carbon monoxide between 0.01 and 0.07 x 10(9)/M.s, and for nitric oxide between 0.12 and 0.25 x 10(9)/M.s. The dissociation velocities for oxygen range from 5 to 25/s, and for CO from 0.005 to 0.011 s. The oxygen dissociation constants range only from 36 to 78 nM. Nanosecond relaxation experiments show large differences between the proteins. Five have known primary structures which correlate closely with the nanosecond relaxations and less immediately with the millisecond reactions. The relevant amino acid substitutions are concentrated in the C-E interhelical region.
Gibson
Q H
QH
Department of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853.
Wittenberg
J B
JB
Wittenberg
B A
BA
Bogusz
D
D
Appleby
C A
CA
D000595:Amino Acid Sequence; D002248:Carbon Monoxide / Q000378:metabolism; D007887:Fabaceae; D006420:Hemeproteins / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D007700:Kinetics; D007874:Leghemoglobin / Q000378:metabolism*; D008024:Ligands; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010944:Plants / Q000378:metabolism*; D010946:Plants, Medicinal; D011485:Protein Binding
D006420:Hemeproteins; D006454:Hemoglobins; D007874:Leghemoglobin; D008024:Ligands; D009569:Nitric Oxide; D002248:Carbon Monoxide; D010100:Oxygen