Spectroscopic characterization of a truncated hemoglobin from the nitrogen-fixing bacterium Herbaspirillum seropedicae |
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Authors: | Guilherme Razzera Javier Vernal Debora Baruh Viviane I. Serpa Carolina Tavares Flávio Lara Emanuel M. Souza Fábio O. Pedrosa Fábio C. L. Almeida Hernán Terenzi Ana Paula Valente |
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Affiliation: | 1. Centro Nacional de Ressonancia Magnética Nuclear, Jiri Jonas, Departamento de Bioquímica Médica, ICB/CCS/UFRJ, Rio de Janeiro, RJ, Brazil 3. Laboratório de Express?o Gênica, Departamento de Bioquímica, Universidade Federal de Santa Catarina, Florianópolis, SC, 88040-900, Brazil 2. Lab. de Bioquímica de Artrópodos Hematófagos, Departamento de Bioquímica Médica, ICB/CCS/UFRJ, Rio de Janeiro, RJ, Brazil 4. Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Curitiba, Brazil
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Abstract: | The Herbaspirillum seropedicae genome sequence encodes a truncated hemoglobin typical of group II (Hs-trHb1) members of this family. We show that His-tagged recombinant Hs-trHb1 is monomeric in solution, and its optical spectrum resembles those of previously reported globins. NMR analysis allowed us to assign heme substituents. All data suggest that Hs-trHb1 undergoes a transition from an aquomet form in the ferric state to a hexacoordinate low-spin form in the ferrous state. The close positions of Ser-E7, Lys-E10, Tyr-B10, and His-CD1 in the distal pocket place them as candidates for heme coordination and ligand regulation. Peroxide degradation kinetics suggests an easy access to the heme pocket, as the protein offered no protection against peroxide degradation when compared with free heme. The high solvent exposure of the heme may be due to the presence of a flexible loop in the access pocket, as suggested by a structural model obtained by using homologous globins as templates. The truncated hemoglobin described here has unique features among truncated hemoglobins and may function in the facilitation of O2 transfer and scavenging, playing an important role in the nitrogen-fixation mechanism. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Nuclear magnetic resonance Truncated globin Herbaspirillum seropedicae |
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