Protein Engineering Design & Selection最新文献

Pompe disease is a tissue glycogen disorder caused by genetic insufficiency of the GAA enzyme. GAA enzyme replacement therapies for Pompe disease have been limited by poor lysosomal trafficking of the recombinant GAA molecule through the native mannose-6-phosphate-mediated pathway. Here, we describe the successful rational engineering of a chimeric GAA enzyme that utilizes the binding affinity of a modified IGF-II moiety to its native receptor to bypass the mannose-6-phosphate-mediated lysosomal trafficking pathway, conferring a significant increase in cellular uptake of the GAA enzyme. We also demonstrate the ablation of binding between our modified IGF-II tag and two off-target receptors: IGF-I receptor and insulin receptor, as well as preserved enzymatic activity of the chimeric GAA molecule.

Yeast display is a widely used technology in antibody discovery and protein engineering. The cell size of yeast enables fluorescence-activated cell sorting (FACS) to precisely screen gene libraries, including for multi-parameter selection of protein phenotypes. However, yeast cells show a broader size distribution than mammalian cells that complicates single-cell gate determination for FACS. In this report, we analyze several yeast display gating options in detail and present an optimized strategy to select single yeast cells via flow cytometry. These data reveal optimized single-cell gating strategies to support robust and high-efficiency yeast display studies.

Catalytic antibodies have the ability to bind to and degrade antigens, offering a significant potential for therapeutic use. The light chain of an antibody, UA15-L, can cleave the peptide bond of Helicobacter pylori urease, thus inhibiting the spread of the bacteria. However, the variable domain of UA15-L has a poor thermostability and solubility. In this study, we employed a combined computational and experimental approach to enhance the protein's stability and solubility properties. The protein unfolding hotspots were initially identified using molecular dynamics simulations. Following this, a disulfide bond was designed in an unfolding hotspot to stabilize the protein. Subsequently, protein solubility was enhanced with the assistance of computational methods by introducing polar or charged residues on the protein surface. The combination of multiple mutations resulted in UA15-L variable domain variants with improved thermostability, solubility, expression, and enhanced activity at elevated temperatures. These variants represent promising candidates for further engineering of catalytic activity and specificity.

Recent developments in cancer immunotherapy have highlighted the potential of harnessing natural killer (NK) cells in the treatment of neoplastic malignancies. Of these, bispecific antibodies, and NK cell engager (NKCE) protein therapeutics in particular, have been of interest. Here, we used phage display and yeast surface display to engineer RLN131, a unique cross-reactive antibody that binds to human, mouse, and cynomolgus NKp46, an activating receptor found on NK cells. RLN131 induced proliferation and activation of primary NK cells, and was used to create bispecific NKCE constructs of varying configurations and valency. All NKCEs were able to promote greater NK cell cytotoxicity against tumor cells than an unmodified anti-CD20 monoclonal antibody, and activity was observed irrespective of whether the constructs contained a functional Fc domain. Competition binding and fine epitope mapping studies were used to demonstrate that RLN131 binds to a conserved epitope on NKp46, underlying its species cross-reactivity.

Many proteins do not fold into a fixed three-dimensional structure, but rather function in a highly disordered state. These intrinsically disordered proteins pose a unique challenge to protein engineering and design: How can proteins be designed de novo if not by tailoring their structure? Here, we will review the nascent field of design of intrinsically disordered proteins with focus on applications in biotechnology and medicine. The design goals should not necessarily be the same as for de novo design of folded proteins as disordered proteins have unique functional strengths and limitations. We focus on functions where intrinsically disordered proteins are uniquely suited including disordered linkers, desiccation chaperones, sensors of the chemical environment, delivery of pharmaceuticals, and constituents of biomolecular condensates. Design of functional intrinsically disordered proteins relies on a combination of computational tools and heuristics gleaned from sequence-function studies. There are few cases where intrinsically disordered proteins have made it into industrial applications. However, we argue that disordered proteins can perform many roles currently performed by organic polymers, and that these proteins might be more designable due to their modularity.

Proline-rich antimicrobial peptides (PrAMPs) are attractive antibiotic candidates that target gram-negative bacteria ribosomes. We elucidated the sequence-function landscape of 43 000 variants of a recently discovered family member, Tur1a, using the validated SAMP-Dep platform that measures intracellular AMP potency in a high-throughput manner via self-depletion of the cellular host. The platform exhibited high replicate reproducibility (ρ = 0.81) and correlation between synonymous genetic variants (R2 = 0.93). Only two segments within Tur1a exhibited stringent mutational requirements to sustain potency: residues 9YLP11 and 19FP20. This includes the aromatic residue in the hypothesized binding domain but not the PRP domain. Along with unexpected mutational tolerance of PRP, the data contrast hypothesized importance of the 1RRIR4 motif and arginines in general. In addition to mutational tolerance of residue segments with presumed significance, 77% of mutations are functionally neutral. Multimutant performance mainly shows compounding effects from removed combinations of prolines and arginines in addition to the two segments of residues showing individual importance. Several variants identified as active from SAMP-Dep were externally produced and maintained activity when applied to susceptible species exogenously.

Protein developability is requisite for use in therapeutic, diagnostic, or industrial applications. Many developability assays are low throughput, which limits their utility to the later stages of protein discovery and evolution. Recent approaches enable experimental or computational assessment of many more variants, yet the breadth of applicability across protein families and developability metrics is uncertain. Here, three library-scale assays-on-yeast protease, split green fluorescent protein (GFP), and non-specific binding-were evaluated for their ability to predict two key developability outcomes (thermal stability and recombinant expression) for the small protein scaffolds affibody and fibronectin. The assays' predictive capabilities were assessed via both linear correlation and machine learning models trained on the library-scale assay data. The on-yeast protease assay is highly predictive of thermal stability for both scaffolds, and the split-GFP assay is informative of affibody thermal stability and expression. The library-scale data was used to map sequence-developability landscapes for affibody and fibronectin binding paratopes, which guides future design of variants and libraries.