High-Affinity Binding of the Staphylococcal HarA Protein to Haptoglobin and Hemoglobin Involves a Domain with an Antiparallel Eight-Stranded β-Barrel Fold
| Autor: | Agnieszka Dryla, Walter Koppensteiner, Eszter Nagy, Dieter Gelbmann, Andreas Meinke, Markus Hanner, Annaliesa S. Anderson, Alexander von Gabain, Bernd Hoffmann, Robert Konrat, Carmen Giefing |
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| Rok vydání: | 2007 |
| Předmět: |
Models
Molecular Protein Folding Staphylococcus aureus Magnetic Resonance Spectroscopy Molecular Sequence Data Plasma protein binding Biology Antiparallel (biochemistry) Microbiology Chromatography Affinity Hemoglobins Bacterial Proteins Amino Acid Sequence Binding site Cation Transport Proteins Molecular Biology Haptoglobin binding Binding Sites Haptoglobins Binding protein Membrane Proteins Enzymes and Proteins Protein Structure Tertiary Biochemistry Membrane protein Protein folding Sequence Alignment Protein Binding Binding domain |
| Zdroj: | Journal of Bacteriology. 189:254-264 |
| ISSN: | 1098-5530 0021-9193 |
| DOI: | 10.1128/jb.01366-06 |
| Popis: | Iron scavenging from the host is essential for the growth of pathogenic bacteria. In this study, we further characterized two staphylococcal cell wall proteins previously shown to bind hemoproteins. HarA and IsdB harbor homologous ligand binding domains, the so called NEAT domain (for “near transporter”) present in several surface proteins of gram-positive pathogens. Surface plasmon resonance measurements using glutathione S -transferase (GST)-tagged HarAD1, one of the ligand binding domains of HarA, and GST-tagged full-length IsdB proteins confirmed high-affinity binding to hemoglobin and haptoglobin-hemoglobin complexes with equilibrium dissociation constants ( K D ) of 5 to 50 nM. Haptoglobin binding could be detected only with HarA and was in the low micromolar range. In order to determine the fold of this evolutionarily conserved ligand binding domain, the untagged HarAD1 protein was subjected to nuclear magnetic resonance spectroscopy, which revealed an eight-stranded, purely antiparallel β-barrel with the strand order (-β1 ↓ -β2 ↑ -β3 ↓ -β6 ↑ -β5 ↓ -β4 ↑ -β7 ↓ -β8 ↑ ), forming two Greek key motifs. Based on structural-homology searches, the topology of the HarAD1 domain resembles that of the immunoglobulin (Ig) fold family, whose members are involved in protein-protein interactions, but with distinct structural features. Therefore, we consider that the HarAD1/NEAT domain fold is a novel variant of the Ig fold that has not yet been observed in other proteins. |
| Databáze: | OpenAIRE |
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