Exploring Distinct Conformers of B2-Adrenergic Receptor Via Coarse-Grained Molecular Dynamics Simulations
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Date
2012
Authors
Çakan, Sibel
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Kadir Has Üniversitesi
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Abstract
ß2AR, G protein bağlantılı reseptör ve birçok ilaç için hedef moleküldür. Reseptörünson derece esnek olan yapısı bir çok ligant molekülünü tanıma özelliği sağlar. Sonyıllarda yapılan kristalografik çalışmalar reseptörün aktif ve inaktif yapısını ortayaçıkarmasına rağmen bu çalışmalar reseptörün tüm dinamiğini çözmek için yeterlideğildir. Moleküler dinamik (MD) metodu reseptörün tüm dinamiğini anlamak içinalternatif ve verimli bir yöntemdir. Ancak geleneksel atomistik simülasyonlar birçokbiyolojik olayın gerçekleştiği zaman aralığı olan milisaniye seviyelerine ulaşamaz.Bu nedenle, bu calışmada serbestlik derecesini azaltan kaba taneli modellemekullanıldı. Sistem POPC membran tabakası içine gömülü ß2AR ve sulardanoluşturuldu. CG model kullanılmasının asıl amacı atomistik modellerde mümkünolmayan daha geniş yapısal alanı ortaya çıkarmaktır. Reseptörün bölgesel hareketleriatomistik simülasyonlarla uyum içindedir. CG simülasyondan dört görüntü seçilmişve geri eşleme yöntemi ile atomistik modele çevrilmiştir. Daha sonra herbiri 100 nsuzunluğunda bir MD simülasyonuna tabi tutulmuştur. Enerjik ve yapısal olarak farklıreseptör yapıları ortaya çıkmıştır. CG MD simülasyonunun PCA analizi, ilk beşbirincil bileşenin tüm dinamiğin %50 sini açıklarken, atomistik simülasyonların %85ini açıkladığını göstermiştir. CG ve atomistik öz-vektörlerin maksimum örtüşmedeğeri 0.46 dır. CG modelde atomistik modele göre korelasyonlar daha zayıftır.
ß2 adrenergic receptor (ß2AR) is a G protein-coupled receptor, which belongs to thelargest family of membrane proteins and is the target of many drugs. ß2AR is highlyflexible and, able to recognize a wide range of ligands through its conformationalvariations. Although recent crystallographic experiments have revealed active andinactive conformations, they are not sufficient for deciphering the whole receptor?sdynamics. Molecular dynamics (MD) simulation is an alternative and efficientmethod to understand the protein dynamics. However, traditional all-atomsimulations do not reach the millisecond time scales at which many biologicalprocesses occur. Thus, coarse-grained (CG) modeling is used to reduce the numberof degrees of freedom. The system was composed of ß2AR embedded into apalmitoyl-oleoyl-phosphatidylcholine (POPC) membrane bilayer with surroundingwater. Main purpose of using a CG model is to explore a wider conformational spacethat would not be reachable via all-atom models. The local fluctuations were in goodagreement with all-atom simulations. Four snapshots were selected and reversemappedto all-atom representations. Each was later subjected to 100 ns MDsimulation for equilibration. RMSD clustering yielded distinct receptor conformersthat are both energetically and structurally acceptable. PCA analysis of CG-MDsimulations showed that the first five principle modes explained only 50% of theoverall dynamics compared to 85% in all-atom simulations. Maximum overlap valuebetween eigenvectors of CG and all-atom was determined as 0.46. Normalizedorientational cross-correlations between residue fluctuations revealed weakercorrelations in CG simulations compared to all-atomAPPEND
ß2 adrenergic receptor (ß2AR) is a G protein-coupled receptor, which belongs to thelargest family of membrane proteins and is the target of many drugs. ß2AR is highlyflexible and, able to recognize a wide range of ligands through its conformationalvariations. Although recent crystallographic experiments have revealed active andinactive conformations, they are not sufficient for deciphering the whole receptor?sdynamics. Molecular dynamics (MD) simulation is an alternative and efficientmethod to understand the protein dynamics. However, traditional all-atomsimulations do not reach the millisecond time scales at which many biologicalprocesses occur. Thus, coarse-grained (CG) modeling is used to reduce the numberof degrees of freedom. The system was composed of ß2AR embedded into apalmitoyl-oleoyl-phosphatidylcholine (POPC) membrane bilayer with surroundingwater. Main purpose of using a CG model is to explore a wider conformational spacethat would not be reachable via all-atom models. The local fluctuations were in goodagreement with all-atom simulations. Four snapshots were selected and reversemappedto all-atom representations. Each was later subjected to 100 ns MDsimulation for equilibration. RMSD clustering yielded distinct receptor conformersthat are both energetically and structurally acceptable. PCA analysis of CG-MDsimulations showed that the first five principle modes explained only 50% of theoverall dynamics compared to 85% in all-atom simulations. Maximum overlap valuebetween eigenvectors of CG and all-atom was determined as 0.46. Normalizedorientational cross-correlations between residue fluctuations revealed weakercorrelations in CG simulations compared to all-atomAPPEND
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Biyoteknoloji, Biotechnology
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109