title: Ligand binding to a hemoprotein lacking the distal histidine. The myoglobin from aplysia limacina (Val(E7)).
abstract: The time course of ligand recombination to the myoglobin from Aplysia limacina, which has Val(E7), was measured following photolysis by flashes of 35 ps to 300 ns with a time resolution of 10 ps or 1 ns. CO shows only biomolecular recombination. O2 has a small geminate reaction with a half-time of tens of picoseconds, but no nanosecond geminate reaction. NO has two picosecond relaxations with half-times of 70 ps (15%) and 1 ns (80%) and one nanosecond relaxation with a half-time of 4.6 ns. The biomolecular rates for O2 and NO are the same: 2 x 10(7) M-1 s-1. Methyl and ethyl isonitriles have a geminate reaction with a half-time of 35 ps. Ethyl isonitrile has, in addition, a nanosecond relaxation (25%) with a half-time of 100 ns. t-Butyl isonitrile has four geminate relaxations (10 ps, 35 ps, 1 ns, and 1 microseconds). Analysis of the results suggests much easier movement of ligand between the heme pocket and the exterior than in sperm whale myoglobin (His(E7]. The reactivity of the heme is little different, placing the effect of the differences from sperm whale myoglobin on the distal side of the heme.
authors.affiliation: Centro di Biologie Molecolare del Consiglio Nationale delle Ricerche, Universitá La Sapienza, Roma, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Bellelli
authors.forename: R S
authors.initials: RS
authors.lastname: Blackmore
authors.forename: Q H
authors.initials: QH
authors.lastname: Gibson
mesh_terms: D000818:Animals; D001048:Aplysia / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008433:Mathematics; D009211:Myoglobin / Q000235:genetics / Q000378:metabolism*; D009570:Nitriles / Q000378:metabolism; D010782:Photolysis; D011485:Protein Binding; D013053:Spectrophotometry; D013997:Time Factors; D014633:Valine
chemical_list: D008024:Ligands; D009211:Myoglobin; D009570:Nitriles; D014633:Valine