Cooperative mechanism in the homodimeric myoglobin from Nassa mutabilis

Massimo Coletta, Paolo Ascenzi, Francesca Polizio, Giulietta Smulevich, Rosanna Del Gaudio, Marina Piscopo, Giuseppe Geraci

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Abstract

Oxygen binding and spectroscopic properties of the homodimeric myoglobin (Mb) from the prosobranchia sea snail Nassa mutabilis have been investigated. Oxygen equilibrium curves are pH-independent and cooperative with P50 = 5 ± 1 mmHg and n ≃ 1.5. Circular dichroism spectra of the oxygenated and deoxygenated form of N. mutabilis Mb are superimposable between 190 and 250 nm, suggesting a mechanism for cooperative ligand binding that does not involve changes in the α-helical content of the whole protein. The oxygen dissociation process is biphasic and pH-dependent, with different pK(a) values (=6.7 ± 0.2 and 8.5 ± 0.3) for the two phases. Moreover, the activation energy is essentially the same for both oxygen dissociation processes (E(a) = 56.4 ± 2.1 kJ/mol for the fast phase, and E(a) = 53.8 ± 1.9 kJ/mol for the slow phase), indicating that the rate difference for O2 dissociation between the diliganded and the monoliganded species is mostly dependent on a variation of the activation entropy. Ferrous nitrosylated N. mutabilis Mb shows, at alkaline and neutral pH, axial and rhombic X-band EPR signals, respectively, which display below pH 6 a three-hyperfine pattern typical of five-coordination. The results presented here suggest that in N. mutabilis Mb the kinetic control of cooperativity operates through a mechanism never observed before in other hemoproteins, which requires a ligand-linked large enhancement for the value of the oxygen association process in a molecule not undergoing changes in quaternary structure.

Original languageEnglish
Pages (from-to)2873-2878
Number of pages6
JournalBiochemistry
Volume37
Issue number9
DOIs
Publication statusPublished - Mar 3 1998

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Myoglobin
Oxygen
Ligands
Snails
Entropy
Circular Dichroism
Oceans and Seas
Paramagnetic resonance
Activation energy
Chemical activation
Association reactions
Molecules
Kinetics
Proteins

ASJC Scopus subject areas

  • Biochemistry

Cite this

Coletta, M., Ascenzi, P., Polizio, F., Smulevich, G., Del Gaudio, R., Piscopo, M., & Geraci, G. (1998). Cooperative mechanism in the homodimeric myoglobin from Nassa mutabilis. Biochemistry, 37(9), 2873-2878. https://doi.org/10.1021/bi9713613

Cooperative mechanism in the homodimeric myoglobin from Nassa mutabilis. / Coletta, Massimo; Ascenzi, Paolo; Polizio, Francesca; Smulevich, Giulietta; Del Gaudio, Rosanna; Piscopo, Marina; Geraci, Giuseppe.

In: Biochemistry, Vol. 37, No. 9, 03.03.1998, p. 2873-2878.

Research output: Contribution to journalArticle

Coletta, M, Ascenzi, P, Polizio, F, Smulevich, G, Del Gaudio, R, Piscopo, M & Geraci, G 1998, 'Cooperative mechanism in the homodimeric myoglobin from Nassa mutabilis', Biochemistry, vol. 37, no. 9, pp. 2873-2878. https://doi.org/10.1021/bi9713613
Coletta M, Ascenzi P, Polizio F, Smulevich G, Del Gaudio R, Piscopo M et al. Cooperative mechanism in the homodimeric myoglobin from Nassa mutabilis. Biochemistry. 1998 Mar 3;37(9):2873-2878. https://doi.org/10.1021/bi9713613
Coletta, Massimo ; Ascenzi, Paolo ; Polizio, Francesca ; Smulevich, Giulietta ; Del Gaudio, Rosanna ; Piscopo, Marina ; Geraci, Giuseppe. / Cooperative mechanism in the homodimeric myoglobin from Nassa mutabilis. In: Biochemistry. 1998 ; Vol. 37, No. 9. pp. 2873-2878.
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