The Membrane Mimetic Affects the Spatial Structure and Mobility of EGFR Transmembrane and Juxtamembrane Domains

The epidermal growth factor receptor (EGFR) is one of the most extensively studied receptor tyrosine kinases, as it is involved in a wide range of cellular processes and severe diseases. Recent works reveal that the single-helix transmembrane domains and cytoplasmic juxtamembrane regions play an important role in the receptor activation process. Here we present the results of our investigation of the spatial structure and mobility of the EGFR transmembrane domain and juxtamembrane regions in various membranelike environments, which shed light on the effects of the membrane physical properties and composition on the behavior of the juxtamembrane domain

Role of Dimerization Efficiency of Transmembrane Domains in Activation of Fibroblast Growth Factor Receptor 3

Mutations in transmembrane (TM) domains of receptor tyrosine kinases are shown to cause a number of inherited diseases and cancer development. Here, we use a combined molecular modeling approach to understand molecular mechanism of effect of G380R and A391E mutations on dimerization of TM domains of human fibroblast growth factor receptor 3 (FGFR3). According to results of Monte Carlo conformational search in the implicit membrane and further molecular dynamics simulations, TM dimer of this receptor is able to form a number of various conformations, which differ significantly by the free energy of association in a full-atom model bilayer. The aforementioned mutations affect dimerization efficiency of TM segments and lead to repopulation of conformational ensemble for the dimer. Particularly, both mutations do not change the dimerization free energy of the predominant (putative “non-active”) symmetric conformation of TM dimer, while affect dimerization efficiency of its asymmetric (“intermediate”) and alternative symmetric (putative “active”) models. Results of our simulations provide novel atomistic prospective of the role of G380 and A391E mutations in dimerization of TM domains of FGFR3 and their consecutive contributions to the activation pathway of the receptor

Structural plasticity and thermal stability of the histone-like protein from <i>Spiroplasma melliferum</i> are due to phenylalanine insertions into the conservative scaffold

<p>The histone-like (HU) protein is one of the major nucleoid-associated proteins of the bacterial nucleoid, which shares high sequence and structural similarity with IHF but differs from the latter in DNA-specificity. Here, we perform an analysis of structural-dynamic properties of HU protein from <i>Spiroplasma melliferum</i> and compare its behavior in solution to that of another mycoplasmal HU from <i>Mycoplasma gallisepticum</i>. The high-resolution heteronuclear NMR spectroscopy was coupled with molecular-dynamics study and comparative analysis of thermal denaturation of both mycoplasmal HU proteins. We suggest that stacking interactions in two aromatic clusters in the HUSpm dimeric interface determine not only high thermal stability of the protein, but also its structural plasticity experimentally observed as slow conformational exchange. One of these two centers of stacking interactions is highly conserved among the known HU and IHF proteins. Second aromatic core described recently in IHFs and IHF-like proteins is considered as a discriminating feature of IHFs. We performed an electromobility shift assay to confirm high affinities of HUSpm to both normal and distorted dsDNA, which are the characteristics of HU protein. MD simulations of HUSpm with alanine mutations of the residues forming the non-conserved aromatic cluster demonstrate its role in dimer stabilization, as both partial and complete distortion of the cluster enhances local flexibility of HUSpm.</p

The Conformation of the Epidermal Growth Factor Receptor Transmembrane Domain Dimer Dynamically Adapts to the Local Membrane Environment

The epidermal growth factor receptor (EGFR) family is an important class of receptor tyrosine kinases, mediating a variety of cellular responses in normal biological processes and in pathological states of multicellular organisms. Different modes of dimerization of the human EGFR transmembrane domain (TMD) in different membrane mimetics recently prompted us to propose a novel signal transduction mechanism based on protein–lipid interaction. However, the experimental evidence for it was originally obtained with slightly different TMD fragments used in the two different mimetics, compromising the validity of the comparison. To eliminate ambiguity, we determined the nuclear magnetic resonance (NMR) structure of the bicelle-incorporated dimer of the EGFR TMD fragment identical to the one previously used in micelles. The NMR results augmented by molecular dynamics simulations confirm the mutual influence of the TMD and lipid environment, as is required for the proposed lipid-mediated activation mechanism. They also reveal the possible functional relevance of a subtle interplay between the concurrent processes in the lipid and protein during signal transduction