PMID:11847279
| Citation |
Kwon, K, Streaker, ED and Beckett, D (2002) Binding specificity and the ligand dissociation process in the E. coli biotin holoenzyme synthetase. Protein Sci. 11:558-70 |
|---|---|
| Abstract |
The binding of the Escherichia coli biotin holoenzyme synthetase to the two ligands, biotin and bio-5'-AMP, is coupled to disorder-to-order transitions in the protein. In the structure of the biotin complex, a "glycine-rich" loop that is disordered in the apo-enzyme is folded over the ligand. Mutations in three residues in this loop result in significant changes in the affinity of the enzyme for both biotin and bio-5'-AMP. The kinetic basis of these losses in the affinity resides primarily in changes in the unimolecular rates of dissociation of the complexes. In this work, isothermal titration calorimetry has been employed to examine the detailed thermodynamics of binding of three loop mutants to biotin and bio-5'-AMP. The energetic features of dissociation of the protein*ligand complexes also have been probed by measuring the temperature dependencies of the unimolecular dissociation rates. Analysis of the data using the Eyring formalism yielded entropic and enthalpic contributions to the energetic barrier to dissociation. The thermodynamic results coupled with the known structures of the apo-enzyme and biotin complex have been used to formulate a model for progression from the ground-state complex to the transition state in biotin dissociation. In this model, the transition-state is characterized by both partial disruption of noncovalent bonds and acquisition of some of the disorder that characterizes the glycine-rich loop in the absence of ligand. |
| Links |
PubMed PMC2373468 Online version:10.1110/ps.33502 |
| Keywords |
Adenosine Monophosphate/analogs & derivatives; Adenosine Monophosphate/metabolism; Amino Acid Substitution; Bacterial Proteins/chemistry; Bacterial Proteins/metabolism; Biotin/analogs & derivatives; Biotin/metabolism; Carbon-Nitrogen Ligases/chemistry; Carbon-Nitrogen Ligases/metabolism; Escherichia coli/enzymology; Escherichia coli Proteins; Kinetics; Ligands; Mutation; Protein Binding; Repressor Proteins; Thermodynamics; Transcription Factors |
| edit table |
Significance
You can help EcoliWiki by summarizing why this paper is useful
Useful Materials and Methods
You can help Ecoliwiki by describing the useful materials (strains, plasmids, antibodies, etc) described in this paper.
Annotations
<annotationlinks/>
EcoliWiki Links
Add links to pages that link here (e.g. gene, product, method pages)
References
See Help:References for how to manage references in EcoliWiki.