title: Ligand binding in a hierarchy of globin complexes. The hexagonal bilayer hemoglobin of Lumbricus terrestris and its heme-containing subunits.
abstract: The kinetics of CO and NO recombination with the giant approximately 3600-kDa hexagonal bilayer hemoglobin of Lumbricus terrestris and its subunits, the approximately 200-kDa dodecamer of globin chains (3 x chains (I + II + III + IV] (see preceding paper (Vinogradov S.N., Sharma, P.K., Qabor, A.N., Wall, J.S., Westrick, J.A., Simmons, J.H., and Gill, S.J. (1991) J. Biol. Chem. 266, 13091-13096], the 50-kDa disulfide-bonded trimer (chains II-IV), the monomer (chain I), and the approximately 30-kDa linker (chains VA, VB, and VI), were measured following photolysis over time scales ranging from picosecond to millisecond. CO recombination at 436 nm subsequent to excitation (9 ns) at 532 nm showed three phases covering a 100-fold range for the Hb, dodecamer, trimer, and linker protein. The proportion of the fast phase was 0.1-0.2 for the trimer, dodecamer, and Hb. The relative rates and amplitudes of the phases were not affected by changes in CO concentration or excitation intensity. The monomer showed a single phase with a rate of 2 x 10(6) M-1 s-1. The second-order reaction with NO showed two rates. The faster rate was 90 x 10(6) M-1 s-1 and accounted for approximately 0.7 of the reaction for all species except the monomer, where it accounted for the full reaction. The slower rate was 15 x 10(6) M-1 s-1 for all species except the monomer.
authors.affiliation: Department of Biochemistry and Molecular and Cell Biology, Cornell University, Ithaca, New York 14853.
authors.forename: Q H
authors.initials: QH
authors.lastname: Gibson
authors.forename: R S
authors.initials: RS
authors.lastname: Blackmore
authors.forename: R
authors.initials: R
authors.lastname: Regan
authors.forename: P K
authors.initials: PK
authors.lastname: Sharma
authors.forename: S N
authors.initials: SN
authors.lastname: Vinogradov
mesh_terms: D000818:Animals; D002263:Carboxyhemoglobin / Q000378:metabolism; D005914:Globins / Q000302:isolation & purification / Q000378:metabolism*; D006418:Heme / Q000032:analysis; D006454:Hemoglobins / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D046911:Macromolecular Substances; D008970:Molecular Weight; D009835:Oligochaeta / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D006454:Hemoglobins; D008024:Ligands; D046911:Macromolecular Substances; D006418:Heme; D005914:Globins; D002263:Carboxyhemoglobin