ABSTRACT
In the present paper the interaction mechanism and mode of biologically active cysteine dipeptide (Cys-Cys) with DNA was studied by UV-Vis spectrophotometry and fluorescence spectroscopy using ethidium bromide as a fluorescence probe. The results showed that in the buffer solution of Tris-HCl (pH 7.20), at low concentration of Cys-Cys, the ultraviolet spectrum of DNA-Cys-Cys system produced hypochromic effect with increasing the concentration of Cys-Cys. When the concentration of Cys-Cys increased to some high extent, the ultraviolet spectrum of DNA-Cys-Cys system produced hyperchromic effect. Salt-effect experiment showed that the interaction is liable to be affected by the ionic strengths, suggesting the existence of electrostatic binding between Cys-Cys and DNA. The fluorescence of EB-DNA had quenching effect with increasing the concentration of Cys-Cys, and the Stern-Volmer equation indicated that the quenching process was a static one. According to the Lineweaver-Burk equation the binding constant was determined to be 1.640 x 10(4) L x mol(-1). From the above results it can be concluded that the interaction mode of Cys-Cys with DNA was mainly electrostatic binding. These findings could contribute to further investigation on the mechanism of oligopeptides interaction with DNA.
Subject(s)
Cysteine/chemistry , DNA/chemistry , Spectrometry, Fluorescence , Fluorescent Dyes/chemistryABSTRACT
The use of synthetic oligonucleotides and their mimics to inhibit gene expression by hybridizing with their target sequences has been hindered by their poor cellular uptake and inability to reach the nucleus. Covalent postsynthesis or solid-phase conjugation of peptides to oligonucleotides offers a possible solution to these problems. As feasible chemistry is a prerequisite for biological studies, development of efficient and reproducible approaches for convenient preparation of peptide-oligonucleotide conjugates has become a subject of considerable importance. The present review gives an account of the main synthetic methods available to prepare covalent conjugation of peptides to oligonucleotides.
Subject(s)
Oligonucleotides/chemistry , Oligonucleotides/chemical synthesis , Peptides/chemistry , Peptides/chemical synthesisABSTRACT
ZNF191, a new human zinc finger protein, probably relates to some hereditary diseases and cancers. To obtain structural information of zinc finger domain a convenient method for obtaining milligram quantities of each zinc finger peptide of ZNF191 is necessary. Here, we report an Escherichia coli expression system for rapid and high-level expression of zinc finger 3 and zinc finger 4 of ZNF191. The gene of zinc finger 3 or zinc finger 4 was cloned into pET31b vector to allow expression of single zinc finger peptide as a ketosteroid isomerase (KSI) fusion protein. The KSI-single zinc finger fusion protein was overexpressed in the form of inclusion body, which can be purified by washing several times using buffer solutions, and then be cleaved directly by cyanogen bromide to release single zinc finger peptide. The more than 20mg/L yield of single zinc finger peptide was achieved with more than 95% purity by using YM ultrafiltration membranes. Circular dichroism spectra of these two single zinc finger peptides titrated with Zn(2+) ions demonstrate that they have different secondary structures.
Subject(s)
Kruppel-Like Transcription Factors/chemistry , Kruppel-Like Transcription Factors/metabolism , Peptide Fragments/isolation & purification , Peptide Fragments/metabolism , Zinc Fingers , Buffers , Circular Dichroism , Cloning, Molecular , Cyanogen Bromide/pharmacology , Electrophoresis, Polyacrylamide Gel , Escherichia coli/genetics , Formates/pharmacology , Freeze Drying , Genetic Vectors , Histidine/chemistry , Humans , Hydrogen-Ion Concentration , Inclusion Bodies/metabolism , Kruppel-Like Transcription Factors/genetics , Membranes, Artificial , Peptide Fragments/chemistry , Peptide Fragments/genetics , Plasmids , Protein Structure, Secondary , Protein Structure, Tertiary , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/isolation & purification , Recombinant Fusion Proteins/metabolism , Sequence Analysis, DNA , Solutions/chemistry , Spectrometry, Mass, Electrospray Ionization , Ultrafiltration , Zinc/chemistryABSTRACT
The gene coding for the lipase-solubilized bovine liver microsomal cytochrome b5 (cyt b5) was expressed in Escherichia coli BL21 cells as a glutathione S-transferase fusion protein (GST-cyt b5) using the constructed expression vector pGEX-cyt b). The GST-cyt b5 fusion protein can be matured in vivo as a holoprotein with heme incorporated into cyt b5 during the fermentation, and the purification procedures were simplified by using a one-step affinity column chromatography with glutathione-agarose gel. The fusion protein was characterized by its spectroscopic and electrochemical properties, the interaction between GST-cyt b5 and cyt c was also investigated. The results show that GST-cyt b5 fusion protein shares similar properties and functions to that of isolated cyt b5. Although cyt b5 and GST were fused together, the two partners have not made significant structural and functional alterations of their counterparts, the protein-protein interactions between them are apparently very weak. To our knowledge, the present study is the first report to express cyt b5 as a GST-cyt b5 fusion protein, which provides a good example for the in vivo maturation of a hemoprotein as a GST fusion protein and sheds new light on the protein-protein interactions within the GST fusion protein.
