ABSTRACT. The aim of this study was to analyze the effect of linker length on the expression and biological activity of recombinant protein onconase (ONC) in fusion with human serum albumin (HSA) in Pichia pastoris. Four flexible linkers with different lengths namely Linker L0, L1: (GGGGS) 1 , L2: (GGGGS) 2 , and L3:(GGGGS) 3 were inserted into the fusion gene and referred to as HSA-n-ONC, where N = 0, 5, 10, or 15. The sequence of the fusion gene HSA-ONC was designed based on the GC content and codon bias in P. pastoris; the signal peptide of albumin was used as the secretion signal. Gene sequences coding for the fusion protein with different linkers were inserted into pPICZα-A to form recombinant plasmids pPICZα-A/HSA-n-ONC, which were then transformed into P. pastoris X-33 for protein expression. Ideal conditions for expression of the fusion proteins were optimized at a small scale, using shake flasks before proceeding to mass production in 10-L fermenters. The recombinant fusion proteins 19361Linker length affects HSA-fused ONC in P. pastoris ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (4): 19360-19370 (2015) were purified by aqueous two-phase extraction coupled with DEAE anion exchange chromatography, and their cytotoxic effect on the tumor cell was evaluated by the sulforhodamine B assay. The results showed that the expressed amount of fusion proteins had no significant relationship with the length of different linkers and rHSA-0-ONC had no cytotoxic effect on the tumor cells. While rHSA-5-ONC and rHSA-10-ONC had a weak cytotoxic effect, rHSA-15-ONC could kill various tumor cells in vitro. In summary, the biological activity of the fusion protein gradually improved with increasing length of the linker.
Differential drug response, that is, pharmacodynamics, is most often likely to be a complex trait, controlled by the combined influences of multiple genes and environmental influences. Genetic mapping has proven to be a powerful tool for detecting and identifying specific genes affecting complex traits, that is, quantitative trait loci (QTL), based on polymorphic markers. In this article, we present a novel statistical model for genetic mapping of QTL governing pharmacodynamic processes. In principle, this model is a combination of functional mapping proposed to map function-valued traits and linkage disequilibrium mapping designed to provide high-resolution mapping of QTL by making use of recombination events created at a historic time. We implement a closed-form solution for the Expectation-Maximization algorithm to estimate the population genetic parameters of QTL and the simplex algorithm to estimate the curve parameters describing the pharmacodynamic changes of different QTL genotypes in response to drug dose or concentrations. Extensive simulations are performed to investigate the statistical properties of our model. The implications of our model in pharmacogenetic and pharmacogenomic research are discussed.
Substrate-based probes utilize known substrate specificity parameters to create a probe that can be activated by a target enzyme. In developing probes for heparanase, an endo-beta-glucuronidase, we previously reported that small, inactive substrate-based probes could be electronically tuned by incorporating electron-withdrawing atoms on the aromatic aglycone fluorophore, ortho- to the cleaved glycosidic bond. However, the installation of electron-withdrawing groups directly onto established fluorophores or other reporters complicates the synthesis of new heparanase probes. In this work we report a new design strategy to expand the toolkit of heparanase imaging probes, in which the installation of an electronically tuned benzyl alcohol linker restored the activity of a previously inactive heparanase probe using 4-methylumbelliferone as the fluorescent reporter, suggesting such a linker can provide a scaffold for facile development of activatable heparanase probes bearing a variety of imaging moieties.
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