Picosecond geminate recombination of CO to the complexes calmodulin*heme-CO and calmodulin*heme-CO*melittin.
Picosecond CO recombination kinetics have been measured after photodissociation of the artificial complexes calmodulin*heme-CO and calmodulin*heme-CO*melittin. These systems show an enhancement of the geminate fraction of kinetics relative to unbound heme-CO, due in part to fast geminate kinetics (tau=50ps for the initial phase), as well as a decrease in the rate of migration of CO away from the binding site. This indicates that calmodulin provides a complete pocket around the heme group. Rather than competing with the hemes for binding to calmodulin, the melittin seems to act as a cap to further enclose the hemes; melittin increases the affinity of calmodulin for heme-CO, but only weakly affects the CO recombination kinetics.
Leclerc-L'Hostis
E
E
INSERM U299, Hôpital de Bicêtre, Le Kremlin Bicêtre, France.
Franzen
S
S
Lambry
J C
JC
Martin
J L
JL
Leclerc
L
L
Poyart
C
C
Marden
M C
MC
D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry / Q000494:pharmacology; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism; D002248:Carbon Monoxide / Q000737:chemistry* / Q000378:metabolism; D006418:Heme / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008555:Melitten / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D010782:Photolysis; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D014783:Viscosity
D002147:Calmodulin; D008555:Melitten; D006418:Heme; D002248:Carbon Monoxide; D002118:Calcium