Ligand binding to a hemoprotein lacking the distal histidine. The myoglobin from aplysia limacina (Val(E7)).

• Published in: Journal of Biological Chemistry
• Main Authors: R S Blackmore, Q H Gibson, Andrea Bellelli
• Format: Article in Journal/Newspaper
• Language: English
• Published: 1990
• Subjects: Cell Biology; Molecular Biology; Biochemistry; Sperm whale
• Online Access: https://www.openaccessrepository.it/record/89509; https://doi.org/10.1016/s0021-9258(18)77390-0

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.