Non-robotic high-throughput setup for manual assembly of nanolitre vapour-diffusion protein crystallization screens

Cost-Effective Protein Production in CHO Cells Following Polyethylenimine-Mediated Gene Delivery Showcased by the Production and Crystallization of Antibody Fabs

Laboratory production of recombinant mammalian proteins, particularly antibodies, requires an expression pipeline assuring sufficient yield and correct folding with appropriate posttranslational modifications. Transient gene expression (TGE) in the suspension-adapted Chinese Hamster Ovary (CHO) cell lines has become the method of choice for this task. The antibodies can be secreted into the media, which facilitates subsequent purification, and can be glycosylated. However, in general, protein production in CHO cells is expensive and may provide variable outcomes, namely in laboratories without previous experience. While achievable yields may be influenced by the nucleotide sequence, there are other aspects of the process which offer space for optimization, like gene delivery method, cultivation process or expression plasmid design. Polyethylenimine (PEI)-mediated gene delivery is frequently employed as a low-cost alternative to liposome-based methods. In this work, we are proposing a TGE platform for universal medium-scale production of antibodies and other proteins in CHO cells, with a novel expression vector allowing fast and flexible cloning of new genes and secretion of translated proteins. The production cost has been further reduced using recyclable labware. Nine days after transfection, we routinely obtain milligrams of antibody Fabs or human lactoferrin in a 25 mL culture volume. Potential of the platform is established based on the production and crystallization of antibody Fabs and their complexes.

Crystallization and preliminary X-ray diffraction analysis of tau protein microtubule-binding motifs in complex with Tau5 and DC25 antibody Fab fragments

The Alzheimer's disease-associated protein tau is an intrinsically disordered protein with no preferred structure in solution. Under physiological conditions, tau binds to microtubules and regulates their dynamics, whereas during the development of neurodegeneration tau dissociates from microtubules, misfolds and creates highly insoluble deposits. To elucidate the determinants of tau-protein misfolding, tau peptides from microtubule-binding motifs were crystallized in complexes with Fab fragments of specific monoclonal antibodies. The crystals diffracted to 1.69 Å resolution and gave complete data sets using a synchrotron X-ray source. Molecular replacement was used to solve the phase problem.