2rs4
NMR structure of stereo-array isotope labelled (SAIL) peptidyl-prolyl cis-trans isomerase from E. coli (EPPIb)
Structural highlights
FunctionPPIB_ECOLI PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. Publication Abstract from PubMedWe recently developed new NMR methods for monitoring the hydrogen exchange rates of tyrosine hydroxyl (Tyr-OH) and cysteine sulfhydryl (Cys-SH) groups in proteins. These methods facilitate the identification of slowly exchanging polar side-chain protons in proteins, which serve as sources of NOE restraints for protein structure refinement. Here, we have extended the methods for monitoring the hydrogen exchange rates of the OH groups of serine (Ser) and threonine (Thr) residues in an 18.2 kDa protein, EPPIb, and thus demonstrated the usefulness of NOE restraints with slowly exchanging OH protons for refining the protein structure. The slowly exchanging Ser/Thr-OH groups were readily identified by monitoring the (13)C(beta)-NMR signals in an H(2)O/D(2)O (1:1) mixture, for the protein containing Ser/Thr residues with (13)C, (2)H-double labels at their beta carbons. Under these circumstances, the OH groups exist in equilibrium between the protonated and deuterated isotopomers, and the (13)C(beta) peaks of the two species are resolved when their exchange rate is slower than the time scale of the isotope shift effect. In the case of EPPIb dissolved in 50 mM sodium phosphate buffer (pH 7.5) at 40 degrees C, one Ser and four Thr residues were found to have slowly exchanging hydroxyl groups (k(ex) < approximately 40 s(-1)). With the information for the slowly exchanging Ser/Thr-OH groups in hand, we could collect additional NOE restraints for EPPIb, thereby making a unique and important contribution toward defining the spatial positions of the OH protons, and thus the hydrogen-bonding acceptor atoms. Hydrogen Exchange Study on the Hydroxyl Groups of Serine and Threonine Residues in Proteins and Structure Refinement Using NOE Restraints with Polar Side-Chain Groups.,Takeda M, Jee J, Ono AM, Terauchi T, Kainosho M J Am Chem Soc. 2011 Oct 10. PMID:21955241[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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