Rational design of glycoengineered interferon-ß analogs with improved aggregation state: experimental validation.

Recombinant human interferon-ß (rhIFN-ß) used clinically has lower efficacy than expected due to protein instabilities such as aggregation. Increasing molecular stability, glycoengineering has been used to improve clinical efficacy for a number of therapeutics; however, often labor-intensive trail-and-error approaches are used to identify additional glycosylation sites. In this study two rhIFN-ß analogs with one additional glycosylation site, L6T and S75N, identified by a rational in silico approach, were characterized. These rhIFN-ß analogs were synthesized in parallel with a Chinese hamster ovary (CHO) codon-optimized natural human IFN-ß (Opt-IFN-ß) and expressed in CHO cells using the same expression system. The molecular weights for both analogs were observed to be higher than Opt-IFN-ß, consistent with hyper-glycosylation. The in vitro biological assay showed the hyper-glycosylated analogs and the Opt-IFN-ß had similar activity. The aggregation studies demonstrated that both analogs had lower tendencies to aggregate compared to the Opt-IFN-ß. These experimental studies validate the in silico strategy to predict suitable glycosylation sites that would be glycosylated, while maintaining biological function. Moreover, this work describes hyper-glycosylated rhIFN-ß analogs with improved solubility (i.e. lower aggregation). These findings, together with the rational in silico design, will allow us to increase protein glycosylation with the goal to enhance therapeutic efficacy.

Polarity-based fractionation in proteomics: hydrophilic interaction vs reversed-phase liquid chromatography.

During recent decades, hydrophilic interaction liquid chromatography (HILIC) ahs been introduced to fractionate or purify especially polar solutes such as peptides and proteins while reversed-phase liquid chromatography (RPLC) is also a common strategy. RPLC is also a common dimension in multidimensional chromatography. In this study, the potential of HILIC vs RPLC chromatography was compared for proteome mapping of human peripheral blood mononuclear cell extract. In HILIC a silica-based stationary phase and for RPLC a C18 column were applied. Then separated proteins were eluted to an ion trap mass spectrometry system. Our results showed that the HILIC leads to more proteins being identified in comparison to RPLC. Among the total 181 identified proteins, 56 and 38 proteins were fractionated specifically by HILIC and RPLC, respectively. In order to demonstrate this, the physicochemical properties of identified proteins such as polarity and hydrophobicity were considered. This analysis indicated that polarity may play a major role in the HILIC separation of proteins vs RPLC. Using gene ontology enrichment analysis, it was also observed that differences in physicochemical properties conform to the cellular compartment and biological features. Finally, this study highlighted the potential of HILIC and the great orthogonality of RPLC in gel-free proteomic studies. Copyright © 2015 John Wiley & Sons, Ltd.

Interaction modes and absolute affinities of α-amino acids for Mn2+: a comprehensive picture.

Manganese is involved as a cofactor in the activation of numerous enzymes as well as the oxygen-evolving complex of photosystem II. Full understanding of the role played by the Mn(2+) ion requires detailed knowledge of the interaction modes and energies of manganese with its various environments, a knowledge that is far from complete. To bring detailed insight into the local interactions of Mn in metallopeptides and proteins, theoretical studies employing first-principles quantum mechanical calculations are carried out on [Mn-amino acid](2+) complexes involving all 20 natural α-amino acids (AAs). Detailed investigation of [Mn-serine](2+), [Mn-cysteine](2+), [Mn-phenylalanine](2+), [Mn-tyrosine](2+), and [Mn-tryptophan](2+) indicates that with an electron-rich side chain, the most stable species involves interaction of Mn(2+) with carbonyl oxygen, amino nitrogen, and an electron-rich section of the side chain of the AA in its canonical form. This is in sharp contrast with aliphatic side chains for which a salt bridge is formed. For aromatic AAs, complexation to manganese leads to partial oxidation as well as aromaticity reduction. Despite multisite binding, AAs do not generate strong enough ligand fields to switch the metal to a low- or even intermediate-spin ground state. The affinities of Mn(2+) for all AAs are reported at the B3LYP and CCSD(T) levels of theory, thereby providing the first complete series of affinities for a divalent metal ion. The trends are compared with those of other cations for which affinities of all AAs have been previously obtained.

An efficient procedure for purification of recombinant human ß heat shock protein 90.

BACKGROUND AND THE PURPOSE OF THE STUDY: Heat Shock Protein 90 (Hsp90) is typically the most abundant chaperone in the eukaryotic cell cytoplasm, and its expression is essential for loading immunogenic peptides onto major histocompatibility complex molecules for presentation to T-cells. Therefore, it may act as a good candidate as an adjuvant molecule in vaccine technology. METHODS: Initially the human Hsp90ß gene was cloned into the heat inducible expression vector pGP1-2 and then the recombinant protein was isolated by ion exchange chromatography. After intradermal injection of confirmed purified band of protein to rabbits and isolation of the serum IgG antibody, for its affinity purification, the rabbit's purified Hsp90 specific IgG was coupled to the cyanogen bromide-activated Sepharose 4B. RESULTS: The recovery of the purified protein of interest by affinity chromatography was 50%. CONCLUSION: This research enabled purification of human heat shock protein by a laboratory prepared column chromatography.