Document Detail

Energetics of the Escherichia coli DnaT protein trimerization reaction.
MedLine Citation:
PMID:  23418702     Owner:  NLM     Status:  MEDLINE    
Thermodynamic and structural characteristics of the Escherichia coli DnaT protein trimerization reaction have been quantitatively examined using fluorescence anisotropy and analytical ultracentrifugation methods. Binding of magnesium to the DnaT monomers regulates the intrinsic affinity of the DnaT trimerization reaction. Comparison between the DnaT trimer and the isolated N-terminal core domain suggests that magnesium binds to the N-terminal domain but does not associate with the C-terminal region of the protein. The magnesium binding process is complex and involves approximately three Mg(2+) cations per protein monomer. The observed effect seems to be specific for Mg(2+). In the examined salt concentration range, monovalent cations and anions do not affect the trimer assembly process. However, magnesium affects neither the cooperativity of the trimerization reaction nor the GnHCl-induced trimer dissociation, strongly indicating that Mg(2+) indirectly stabilizes the trimer through the induced changes in the monomer structures. Nevertheless, formation of the trimer also involves specific conformational changes of the monomers, which are independent of the presence of magnesium. Binding of Mg(2+) cations dramatically changes the thermodynamic functions of the DnaT trimerization, transforming the reaction from a temperature-dependent to temperature-independent process. Highly cooperative dissociation of the trimer by GnHCl indicates that both interacting sites of the monomer, located on the N-terminal core domain and formed by the small C-terminal region, are intimately integrated with the entire protein structure. In the intact protein, the C-terminal region most probably interacts with the corresponding binding site on the N-terminal domain of the monomer. Functional implications of these findings are discussed.
Michal R Szymanski; Maria J Jezewska; Wlodzimierz Bujalowski
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2013-03-08
Journal Detail:
Title:  Biochemistry     Volume:  52     ISSN:  1520-4995     ISO Abbreviation:  Biochemistry     Publication Date:  2013 Mar 
Date Detail:
Created Date:  2013-03-19     Completed Date:  2013-05-09     Revised Date:  2014-03-26    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1858-73     Citation Subset:  IM    
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MeSH Terms
DNA-Binding Proteins / chemistry*,  metabolism
Escherichia coli / chemistry*,  metabolism
Escherichia coli Proteins / chemistry*,  metabolism
Guanidine / metabolism
Magnesium / metabolism
Models, Molecular
Protein Binding
Protein Conformation
Protein Multimerization*
Protein Stability
Protein Structure, Tertiary
Grant Support
Reg. No./Substance:
0/DNA-Binding Proteins; 0/DnaT protein, E coli; 0/Escherichia coli Proteins; I38ZP9992A/Magnesium; JU58VJ6Y3B/Guanidine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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