Modulation of the catalytic activity of a metallonuclease by tagging with oligohistidine

His-tag β-galactosidase supramolecular performance

β-Galactosidase is an important biotechnological enzyme used in the dairy industry, pharmacology and in molecular biology. In our laboratory we have overexpressed a recombinant β-galactosidase in Escherichia coli (E. coli). This enzyme differs from its native version (β-Gal_WT) in that 6 histidine residues have been added to the carboxyl terminus in the primary sequence (β-Gal_His), which allows its purification by immobilized metal affinity chromatography (IMAC). In this work we compared the functionality and structure of both proteins and evaluated their catalytic behavior on the kinetics of lactose hydrolysis. We observed a significant reduction in the enzymatic activity of β-Gal_His with respect to β-Gal_WT. Although, both enzymes showed a similar catalytic profile as a function of temperature, β-Gal_His presented a higher resistance to the thermal inactivation compared to β-Gal_WT. At room temperature, β-Gal_His showed a fluorescence spectrum compatible with a partially unstructured protein, however, it exhibited a lower tendency to the thermal-induced unfolding with respect to β-Gal_WT. The distinctively supramolecular arranges of the proteins would explain the effect of the presence of His-tag on the enzymatic activity and thermal stability.

Insights on the emerging biotechnology of histidine-rich peptides

In the late 70's, the discovery of the restriction enzymes made possible the biological production of functional proteins by recombinant DNA technologies, a fact that largely empowered both biotechnological and pharmaceutical industries. Short peptides or small protein domains, with specific molecular affinities, were developed as purification tags in downstream processes to separate the target protein from the culture media or cell debris, upon breaking the producing cells. Among these tags, and by exploiting the interactivity of the imidazole ring of histidine residues, the hexahistidine peptide (H6) became a gold standard. Although initially used almost exclusively in protein production, H6 and related His-rich peptides are progressively proving a broad applicability in novel utilities including enzymatic processes, advanced drug delivery systems and diagnosis, through a so far unsuspected adaptation of their binding capabilities. In this context, the coordination of histidine residues and metals confers intriguing functionalities to His-rich sequences useable in the forward-thinking design of protein-based nano- and micro-materials and devices, through strategies that are comprehensively presented here.

Multiplicity of carotene patterns derives from competition between phytoene desaturase diversification and biological environments

Phytoene desaturases catalyse from two to six desaturation reactions on phytoene, generating a large diversity of molecules that can then be cyclised and produce, depending on the organism, many different carotenoids. We constructed a phylogenetic tree of a subset of phytoene desaturases from the CrtI family for which functional data was available. We expressed in a bacterial system eight codon optimized CrtI enzymes from different clades. Analysis of the phytoene desaturation reactions on crude extracts showed that three CrtI enzymes can catalyse up to six desaturations, forming tetradehydrolycopene. Kinetic data generated using a subset of five purified enzymes demonstrate the existence of characteristic patterns of desaturated molecules associated with various CrtI clades. The kinetic data was also analysed using a classical Michaelis–Menten kinetic model, showing that variations in the reaction rates and binding constants could explain the various carotene patterns observed. Competition between lycopene cyclase and the phytoene desaturases modified the distribution between carotene intermediates when expressed in yeast in the context of the full β-carotene production pathway. Our results demonstrate that the desaturation patterns of carotene molecules in various biological environments cannot be fully inferred from phytoene desaturases classification but is governed both by evolutionary-linked variations in the desaturation rates and competition between desaturation and cyclisation steps.

Preparation of RGD4C fused anti-TNFα nanobody and inhibitory activity on triple-negative breast cancer in vivo

AIMS

Triple-negative breast cancer (TNBC) is not sensitive to current endocrine treatments, so new treatment strategies need to be explored. Based on previous antitumour studies on anti-TNFα nanobody, we designed a novel fusion nanobody to enhance antitumour activity of the anti-TNFα nanobody in TNBC.

MAIN METHODS

The RGD4C contains RGD sequence, which is the smallest recognition unit binding to the αvβ3 receptor on tumour cell membranes and involved in tumour cell adhesion, proliferation, and metastasis. RGD4C was fused to anti-TNFα nanobody to investigate the antitumour activity in vitro and in vivo.

KEY FINDINGS

The antitumour effects of fusion nanobody V-L-R-H could effectively bind to αvβ3 and inhibit cell migration and proliferation of MDA-MB-231, which had satisfying purification efficiency and approving antigen or receptor binding activity. V-L-R-H could inhibit the TNFα-mediated PI3K/AKT/NF-κB signal pathway and integrin αvβ3 correlative FAK focal adhesion signal pathway. Mouse xenograft tumour experiments showed that the V-L-R-H could inhibit tumour proliferation and metastasis; reduce the TNFα, HIFα, Ki67, and CD31 concentrations in tumour; and inhibit the process of epithelial-mesenchymal transition.

SIGNIFICANCE

The fusion nanobody enhanced antitumour activity of the anti-TNFα nanobody on TNBC. It provided a reference for the design of dual functional fusion proteins and development of tumour treatment strategies of antagonistic TNFα and αvβ3, and a new therapeutic strategy and research direction for the treatment of TNBC.