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1

NMR measurements of proton exchange between solvent and peptides and proteins

100%
Wojcik J., Ruszczynska K., Zhukov I., Ejchart A.
Acta Biochimica Polonica
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1999
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tom 46
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nr 3
Scope and limitations of the NMR based methods, equilibration and magnetization transfer, for measuring proton exchange rates of amide protons in peptides and proteins with water protons are discussed. Equilibration is applied to very slow processes detected by hydrogen-deuterium exchange after a solute is dissolved in D2O. Magnetization transfer allows to study moderately rapid processes in H2O. A number of precautions should be undertaken in order to avoid systemic errors inherent in the magnetization transfer method.
2

Cyclic enkephalin-deltorphin hybrids containing a carbonyl bridge: structure and opioid activity

64%
Ciszewska M., Ruszczynska K., Oleszczuk M., Chung N. N., Witkowska E., Schiller P. W., Wojcik J., Izdebski J.
Acta Biochimica Polonica
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2011
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tom 58
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nr 2
 Six hybrid N-ureidoethylamides of octapeptides in which an N-terminal cyclic structure related to enkephalin was elongated by a C-terminal fragment of deltorphin were synthesized on MBHA resin. The synthetic procedure involved deprotection of Boc groups with HCl/dioxane and cleavage of the peptide resin with 45 % TFA in DCM. d-Lys and d-Orn were incorporated in position 2, and Lys, Orn, Dab, or Dap in position 5. The side chains of the dibasic amino function were protected with the Fmoc group. This protection was removed by treatment with 55 % piperidine in DMF, and cyclization was achieved by treatment with bis-(4-nitrophenyl)carbonate. Using various combinations of dibasic amino acids, peptides containing a 17-, 18-, 19- or 20-membered ring structure were obtained. The peptides were tested in the guinea-pig ileum (GPI) and mouse vas deferens (MVD) assays. Diverse opioid activities were observed, depending on the size of the ring. Extension of the enkephalin sequence at the C-terminus by a deltorphin fragment resulted in a change of receptor selectivity in favor of the δ receptor. The conformational propensities of selected peptides were determined using the EDMC method in conjunction with data derived from NMR experiments carried out in water. This approach allowed proper examination of the dynamical behavior of these small peptides. The results were compared with those obtained earlier with corresponding N-(ureidoethyl)pentapeptide amides.
3

Interaction of three Caenorhabditis elegans isoforms of translation initiation factor eIF4E with mono- and trimethylated mRNA 5' cap analogues

64%
Stachelska A., Wieczorek Z., Ruszczynska K., Stolarski R., Pietrzak M., Lamphear B. J., Rhoads R. E., Darzynkiewicz E., Jankowska-Anyszka M.
Acta Biochimica Polonica
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2002
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tom 49
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nr 3
Translation initiation factor eIF4E binds the m G7 cap of eukaryotic mRNAs and me­diates recruitment of mRNA to the ribosome during cap-dependent translation initia­tion. This event is the rate-limiting step of translation and a major target for translational control. In the nematode Caenorhabditis elegans, about 70% of genes express mRNAs with an unusual cap structure containing m3 2,2,7 G, which is poorly rec­ognized by mammalian eIF4E. C. elegans expresses five isoforms of eIF4E (IFE-1, IFE-2, etc.). Three of these (IFE-3, IFE-4 and IFE-5) were investigated by means of spectroscopy and structural modelling based on mouse eIF4E bound to m7GDP. Intrinsic fluorescence quenching of Trp residues in the IFEs by iodide ions indicated structural differences between the apo and m7G cap bound proteins. Fluorescence quenching by selected cap analogues showed that only IFE-5 forms specific complexes with both m7G- and m3 2,2,7 G-containing caps (Kas 2 x 106M–1 to 7 x 106M–1) whereas IFE-3 and IFE-4 discriminated strongly in favor of m7G-containing caps. These spectroscopic results quantitatively confirm earlier qualitative data derived from affinity chromatography. The dependence of Kas on pH indicated optimal cap binding of IFE-3, IFE-4 and IFE-5 at pH 7.2, lower by 0.4 pH units than that of eIF4E from human erythrocytes. These results provide insight into the molecular mechanism of recognition of structurally different caps by the highly homologous IFEs.
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