ABSTRACT
Heavy chain monoclonal antibodies are being considered as alternative to whole-IgG monoclonal antibodies for certain niche applications. Protein-A chromatography which is widely used for purifying IgG monoclonal antibodies is also used for purifying heavy chain monoclonal antibodies as these molecules possess fully functional Fc regions. However, the acidic conditions used to elute bound antibody may sometimes also leach protein-A, which is immunotoxic. Low pH conditions also tend to make the mAb molecules unstable and prone to aggregation. Moreover, protein-A affinity chromatography does not remove aggregates already present in the feed. Hydrophobic interaction membrane chromatography (or HIMC) has already been studied as an alternative to protein-A chromatography for purifying whole-IgG monoclonal antibodies. This paper describes the use of HIMC for capturing a humanized chimeric heavy chain monoclonal antibody (EG2-hFC). Binding and eluting conditions were suitably optimized using pure EG2-hFC. Based on this, an HIMC method was developed for capture of EG2-hFC directly from cell culture supernatant. The EG2-hFc purity obtained in this single-step process was high. The glycan profiles of protein-A and HIMC purified monoclonal antibody samples were similar, clearly demonstrating that both techniques captured similarly glycosylated population of EG2-hFc. Moreover, this technique was able to resolve aggregates from monomeric form of the EG2-hFc.
Subject(s)
Antibodies, Monoclonal/isolation & purification , Chromatography, Liquid/methods , Hydrophobic and Hydrophilic Interactions , Single-Chain Antibodies/isolation & purification , Antibodies, Monoclonal/genetics , Chromatography, Affinity/methods , Humans , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/isolation & purification , Single-Chain Antibodies/geneticsABSTRACT
Polynucleotides containing consecutive tracts of guanines can adopt an intramolecular G-quadruplex structure where multiple planar tetrads of hydrogen-bound guanines stack on top of each other. Remodeling of G-quadruplexes impacts numerous aspects of nucleotide biology including transcriptional and translational control. RNA helicase associated with AU-rich element (RHAU), a member of the ATP-dependent DEX(H/D) family of RNA helicases, has been established as a major cellular quadruplex resolvase. RHAU contains a core helicase domain responsible for ATP binding/hydrolysis/helicase activity and is flanked on either side by N- and C-terminal extensions. The N-terminal extension is required for quadruplex recognition, and we have previously demonstrated complex formation between this domain and a quadruplex from human telomerase RNA. Here we used an integrated approach that includes small angle x-ray scattering, nuclear magnetic resonance spectroscopy, circular dichroism, and dynamic light scattering methods to demonstrate the recognition of G-quadruplexes by the N-terminal domain of RHAU. Based on our results, we conclude that (i) quadruplex from the human telomerase RNA and its DNA analog both adopt a disc shape in solution, (ii) RHAU53-105 adopts a defined and extended conformation in solution, and (iii) the N-terminal domain mediates an interaction with a guanine tetrad face of quadruplexes. Together, these data form the foundation for understanding the recognition of quadruplexes by the N-terminal domain of RHAU.
Subject(s)
DEAD-box RNA Helicases/chemistry , DEAD-box RNA Helicases/metabolism , G-Quadruplexes , RNA/chemistry , RNA/metabolism , Telomerase/chemistry , Telomerase/metabolism , AU Rich Elements , Amino Acid Sequence , Base Sequence , Binding Sites , Circular Dichroism , DEAD-box RNA Helicases/genetics , Humans , Models, Molecular , Molecular Sequence Data , Nuclear Magnetic Resonance, Biomolecular , Nucleic Acid Conformation , Peptide Fragments/chemistry , Peptide Fragments/genetics , Peptide Fragments/metabolism , Protein Conformation , Protein Structure, Tertiary , RNA/genetics , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Substrate Specificity , Telomerase/geneticsABSTRACT
BACKGROUND: COMPcc forms a pentameric left-handed coiled coil that is known to bind hydrophilic signaling molecules such as vitamin D(3), and vitamin A. PRINCIPAL FINDINGS: In an integrated approach we reveal the unique binding properties of COMPcc for saturated and unsaturated fatty acids. Our observations suggest that residues Met33 (gating pore), Thr40/Asn41 (water chamber) and Gln54 (electrostatic trap) are key elements for the binding of fatty acids by COMPcc. In addition, this work characterizes the binding of various fatty acids to COMPcc using fluorescence spectroscopy. Our findings reveal a binding trend within the hydrophobic channel of COMPcc, namely, that is driven by length of the methylene tail and incorporation of unsaturation. CONCLUSION/SIGNIFICANCE: The unique binding properties imply that COMPcc may be involved in signalling functions in which hydrophilic ligands are involved. The pentameric channel is a unique carrier for lipophilic compounds. This opens the exciting possibility that COMPcc could be developed as a targeted drug delivery system.
