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Aplysia limacina myoglobin. Crystallographic analysis at 1.6 A resolution
M Bolognesi1, S Onesti, G Gatti
1Dipartimento di Genetica e Microbiologia, Università di Pavia, Italy.
Journal of Molecular Biology
|February 5, 1989
Summary
The crystal structure of mollusc myoglobin reveals its common globin fold. Its heme iron is not directly contacted by Val63 and lacks water at neutral pH, but binds a hydroxyl ion at pH 9.0.
Area of Science:
- Biochemistry
- Structural Biology
- Biophysics
Background:
- Myoglobin is a vital oxygen-binding protein found in many organisms.
- Understanding myoglobin's structure provides insights into protein function and evolution.
- Aplysia limacina myoglobin offers a unique model for studying invertebrate globin structures.
Purpose of the Study:
- To determine the high-resolution crystal structure of ferric Aplysia limacina myoglobin.
- To analyze the structural features of the heme environment and its interactions.
- To investigate the coordination of the heme iron at different pH levels.
Main Methods:
- Restrained crystallographic refinement.
- X-ray diffraction at 1.6 A resolution.
- Structural analysis of protein and heme coordination.
Main Results:
- The myoglobin structure exhibits the typical globin fold with eight alpha-helices.
- The distal residue Val63 (E7) does not directly contact the heme.
- Heme iron is pentacoordinate at neutral pH, with a hydroxyl ion bound at pH 9.0.
Conclusions:
- Aplysia limacina myoglobin shares structural homology with other globins.
- The heme iron coordination and distal pocket structure influence oxygen binding and reactivity.
- The pH-dependent binding of a hydroxyl ion highlights the dynamic nature of the heme site.