1. Stabilization of triple-helical nucleic acids by basic oligopeptides
V N Potaman, R R Sinden Biochemistry. 1995 Nov 14;34(45):14885-92. doi: 10.1021/bi00045a033.
Intermolecular triplex DNA is stabilized by metal cations and polyamines which reduce repulsion between the negatively charged phosphates of the three nucleic acid strands. We use a quantitative chemical-probing assay involving protection of duplex guanines in a homopyrimidine.homopurine (Py.Pu) sequence from dimethyl sulfate modification to study effects of basic oligopeptides on the stability of triplex DNA. An intermolecular protonated pyrimidine.purine.pyrimidine (Py.Pu*Py) triplex formed readily between a duplex DNA region and a 14-mer pyrimidine triplex-forming oligonucleotide (TFO) at pH 5. The triplex was stabilized at pH by the addition of magnesium ions. In the presence of spermine and lysine-rich peptides, the intermolecular triplex was stabilized up to pH 6.5-7.0. The effective peptide concentration required for stabilization was 10(-5)-10(-2) M. Of the basic peptides studied, pentalysine (Lys-Lys-Lys-Lys-Lys) was the most effective triplex stabilizer. It was effective at concentrations which are lower than those required for Lys-Gly-Lys-Gly-Lys and Lys-Ala-Lys-Ala-Lys and are similar to active concentrations of spermine. Basic peptides were more effective at stabilizing a Py.Pu*Py triplex than a pyrimidine.purine.purine (Py.Pu*Pu) triplex. At 1 mM, Lys-Lys-Lys-Lys-Lys stabilized the Py.Pu*Pu triplex at a level comparable to stabilization by Mn2+ and spermine, whereas Lys-Gly-Lys-Gly-Lys and Lys-Ala-Lys-Ala-Lys resulted in weaker TFO binding. The concentration of TFOs required to form triplex DNA were significantly reduced in the presence of peptides.(ABSTRACT TRUNCATED AT 250 WORDS)
2. Fishing out Methionine-Containing Proteins from Complex Biological Systems Based on a Non-Enzymatic Biochemical Reaction
Dongrui Luan, Aishan Zheng, Xiaonan Gao, Kehua Xu, Bo Tang Nano Lett. 2021 Jan 13;21(1):209-215. doi: 10.1021/acs.nanolett.0c03535. Epub 2020 Dec 4.
Nowadays, it still remains a great challenge to develop a simple, fast, and low-toxic method for identification and separation of proteins from complex biological systems. Herein, a nanocomposite (Fe3O4@Au-Se-peptide) was designed and synthesized to fish out methionine-containing proteins based on a non-enzymatic biochemical reaction, which couples amino groups of lysine with the S-methyl group of methionine in the presence of HOBr. Peptides which contain four lysine residues (Lys-Lys-Lys-Lys-{Se-Cys}) linked to the Fe3O4@Au nanocomposites were used to capture methionine residues efficiently via a S═N cross-linking. The methionine-containing protein was obtained by magnetic separation and released from the Fe3O4@Au-Se-peptide nanocomposites with the influence of H2Se. The HRMS and SDS-PAGE results confirmed the methionine-containing protein could be successfully fished out from a mixture solution. This work provides a useful strategy for recognition and separation of a category of proteins from complex biological systems.
