RESUMEN
M. tuberculosis oxidation sense Regulator (MosR) is a transcriptional regulator from Mycobacterium tuberculosis. It senses the environment oxidation and regulates the expression of a secreted oxidoreductase, thus defending the bacilli against oxidative stress from the phagosome. While most of the members of the Multiple antibiotics resistance Regulator (MarR) family are ligand-responsive, MosR may dissociate from its DNA site upon formation of an intrachain disulphide bond. However, the structure of MosR in its oxidized state is not known, and it is not clear how the formation of this disulphide bond would lead to the conformational changes required for dissociation of the DNA. Nonetheless, MosR presents two crystallographically resolved conformations in its reduced state: bound and unbound to DNA. We managed to simulate MosR unbound to the DNA, both in the presence and in the absence of the disulphide bond. Our results indicate that this disulphide bond precludes the N-terminal residues from adopting a conformation that stands in-between the helix α1 and the DNA binding domain (DBD) from the other chain. Once this conformation is achieved in the reduced state, this DBD detaches from the dimerization domain and becomes more flexible, being able to perform motions with higher amplitude and higher degree of collectivity. Only then, MosR may achieve a conformation where its recognition helices fit into the major grooves of its DNA site. The analysis of the collective motions performed by MosR, during the different situations sampled by the molecular dynamics (MDs), was only possible by the method of filtering harmonic modes with specific frequencies. The frequency of the collective motions performed by the DBD of MosR in the reduced state to achieve a DNA-binding conformation is in the range of 20 to 50 MHz, but it may be associated to more sporadic events since it requires the combination of a suitable conformation of the N-terminal residues.
Asunto(s)
Proteínas Bacterianas/metabolismo , ADN/metabolismo , Simulación de Dinámica Molecular , Factores de Transcripción/metabolismo , Proteínas Bacterianas/química , ADN/química , Movimiento (Física) , Mycobacterium tuberculosis , Oxidación-Reducción , Unión Proteica , Conformación Proteica , Factores de Transcripción/químicaRESUMEN
Antimicrobial peptides are recognized candidates with pharmaceutical potential against epidemic emerging multi-drug resistant bacteria. In this study, we use nuclear magnetic resonance spectroscopy and molecular dynamics simulations to determine the unknown structure and evaluate the interaction with dodecylphosphatidylcholine (DPC) and sodium dodecylsulphate (SDS) micelles with three W6 -Hylin-a1 analogs antimicrobial peptides (HyAc, HyK, and HyD). The HyAc, HyK, and HyD bound to DPC micelles are all formed by a unique α-helix structure. Moreover, all peptides reach the DPC micelles' core, which thus suggests that the N-terminal modifications do not influence the interaction with zwiterionic surfaces. On the other hand, only HyAc and HyK peptides are able to penetrate the SDS micelle core while HyD remains always at its surface. The stability of the α-helical structure, after peptide-membrane interaction, can also be important to the second step of peptide insertion into the membrane hydrophobic core during permeabilization. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.