The First Structure from the Soul/Hbp Family of Heme-binding Proteins, Murine P22hbp.
From: Rede de Química e Tecnologia, Centro de Química Fina e Biotecnologia, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
The Journal of biological chemistry
- Publish Date: Oct 2006
- ISSN: 0021-9258
- Volume: 281
- Issue: 42
- Pages: 31553-61
- Medium: Print
- Language: English
- Citation (JAMA): Dias Jorge S, Macedo Anjos L, Ferreira Gloria C, et al. The First Structure from the Soul/Hbp Family of Heme-binding Proteins, Murine P22hbp.. J. Biol. Chem. Oct 2006;281:31553-61
Abstract
Murine p22HBP, a 22-kDa monomer originally identified as a cytosolic heme-binding protein ubiquitously expressed in various tissues, has 27% sequence identity to murine SOUL, a heme-binding hexamer specifically expressed in the retina. In contrast to murine SOUL, which binds one heme per subunit via coordination of the Fe(III)-heme to a histidine, murine p22HBP binds one heme molecule per subunit with no specific axial ligand coordination of the Fe(III)-heme. Using intrinsic protein fluorescence quenching, the values for the dissociation constants of p22HBP for hemin and protoporphyrin-IX were determined to be in the low nanomolar range. The three-dimensional structure of murine p22HBP, the first for a protein from the SOUL/HBP family, was determined by NMR methods to consist of a 9-stranded distorted beta-barrel flanked by two long alpha-helices. Although homologous domains have been found in three bacterial proteins, two of which are transcription factors, the fold determined for p22HBP corresponds to a novel alpha plus beta fold in a eukaryotic protein. Chemical shift mapping localized the tetrapyrrole binding site to a hydrophobic cleft formed by residues from helix alphaA and an extended loop. In an attempt to assess the structural basis for tetrapyrrole binding in the SOUL/HBP family, models for the p22HBP-protoporphyrin-IX complex and the SOUL protein were generated by manual docking and automated methods.
Mesh Headings (Keywords): Amino Acid Sequence, Animals, Carrier Proteins, Heme, Hemeproteins, Hemin, Humans, Mice, Molecular Sequence Data, Protein Structure, Secondary, Protoporphyrins, Sequence Homology, Amino Acid, Tetrapyrroles
Check for Full Text / PubMed Unique Identifier (PMID): 16905545
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