Background: Recent efforts to understand the basis of protein stability have focused attention on comparative studies of proteins from hyperthermophilic and mesophilic organisms. Most work to date has been on either oligomeric enzymes or monomers comprising more than one domain. Such studies are hampered by the need to distinguish between stabilizing interactions acting between subunits or domains from those acting within domains. In order to simplify the search for determinants of protein stability we have chosen to study the monomeric enzyme indole-3-glycerol phosphate synthase from the hyperthermophilic archaeon Sulfolobus solfataricus (sIGPS), which grows optimally at 90 degrees C.
Results: The 2.0 A crystal structure of sIGPS was determined and compared with the known 2.0 A structure of the IGPS domain of the bifunctional enzyme from the mesophilic bacterium Escherichia coli (eIGPS). sIGPS and eIGPS have only 30% sequence identity, but share high structural similarity. Both are single-domain (beta/alpha)8 barrel proteins, with one (eIGPS) or two (sIGPS) additional helices inserted before the first beta strand. The thermostable sIGPS has many more salt bridges than eIGPS. Several salt bridges crosslink adjacent alpha helices or participate in triple or quadruple salt-bridge clusters. The number of helix capping, dipole stabilizing and hydrophobic interactions is also increased in sIGPS.
Conclusions: The higher stability of sIGPS compared with eIGPS seems to be the result of several improved interactions. These include a larger number of salt bridges, stabilization of alpha helices and strengthening of both polypeptide chain termini and solvent-exposed loops.
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Evidence ID | Analyze ID | Gene/Complex | Systematic Name/Complex Accession | Qualifier | Gene Ontology Term ID | Gene Ontology Term | Aspect | Annotation Extension | Evidence | Method | Source | Assigned On | Reference |
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Evidence ID | Analyze ID | Gene | Gene Systematic Name | Phenotype | Experiment Type | Experiment Type Category | Mutant Information | Strain Background | Chemical | Details | Reference |
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Evidence ID | Analyze ID | Gene | Gene Systematic Name | Disease Ontology Term | Disease Ontology Term ID | Qualifier | Evidence | Method | Source | Assigned On | Reference |
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Evidence ID | Analyze ID | Regulator | Regulator Systematic Name | Target | Target Systematic Name | Direction | Regulation of | Happens During | Regulator Type | Direction | Regulation Of | Happens During | Method | Evidence | Strain Background | Reference |
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Site | Modification | Modifier | Source | Reference |
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Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Allele | Assay | Annotation | Action | Phenotype | SGA score | P-value | Source | Reference | Note |
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Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Assay | Annotation | Action | Modification | Source | Reference | Note |
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Complement ID | Locus ID | Gene | Species | Gene ID | Strain background | Direction | Details | Source | Reference |
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Evidence ID | Analyze ID | Dataset | Description | Keywords | Number of Conditions | Reference |
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