RESUMEN
One of the major challenges in solubilization of membrane proteins is to find the optimal physiological environment for their biophysical studies. EPR spectroscopy is a powerful biophysical technique for studying the structural and dynamic properties of macromolecules. However, the challenges in the membrane protein sample preparation and flexible motion of the spin label limit the utilization of EPR spectroscopy to a majority of membrane protein systems in a physiological membrane-bound state. Recently, lipodisq nanoparticles or styrene-maleic acid copolymer-lipid nanoparticles (SMALPs) have emerged as a membrane mimetic system for investigating the structural studies of membrane proteins. However, its detail characterization for membrane protein studies is still poorly understood. Recently, we characterized the potassium channel membrane protein KCNQ1 voltage sensing domain (KCNQ1-VSD) and KCNE1 reconstituted into lipodisq nanoparticles using EPR spectroscopy. In this study, the potassium channel accessory protein KCNE3 containing flexible N- and C-termini was encapsulated into proteoliposomes and lipodisq nanoparticles and characterized for studying its structural and dynamic properties using nitroxide based site-directed spin labeling EPR spectroscopy. CW-EPR lineshape analysis data indicated an increase in spectral line broadenings with the addition of the styrene-maleic acid (SMA) polymer which approaches close to the rigid limit providing a homogeneous stabilization of the protein-lipid complex. Similarly, EPR DEER measurements indicated an enhanced quality of distance measurements with an increase in the phase memory time (Tm) values upon incorporation of the sample into lipodisq nanoparticles, when compared to proteoliposomes. These results agree with the solution NMR structural structure of the KCNE3 and EPR studies of other membrane proteins in lipodisq nanoparticles. This study along with our earlier studies will provide the reference characterization data that will provide benefit to the membrane protein researchers for studying structural dynamics of challenging membrane proteins.
Asunto(s)
Nanopartículas , Canales de Potasio con Entrada de Voltaje , Humanos , Espectroscopía de Resonancia por Spin del Electrón/métodos , Proteínas de la Membrana/química , Canal de Potasio KCNQ1 , Poliestirenos/química , Marcadores de Spin , Nanopartículas/químicaRESUMEN
Hereditary multiple exostoses (HME) is an autosomal dominant skeletal disorder characterized by the presence of multiple osseous prominences. It can occur sporadically or within families (22 - 56%). Two genes, EXT1 and EXT2 located respectively at 8q24 and 11p11-p12, have been isolated to cause HME. It can cause gross deformity of limbs and growth disturbance which is quite a common complication. Malignant transformation to chondrosarcoma can also occur. Neurological presentations are rare and usually happened due to direct compression of a peripheral nerve or nerve root or less often the spinal cord. This case is possibly the first case of HME described from Bangladesh, presented with dorsal cord compression. Decompression was done and the complaints of myelopathy were improved.