The Fukutin Transmembrane Domain: Capturing the Complexity of the Golgi Apparatus Membrane via Multiscale MD Simulations

Abstract

The membrane of the Golgi apparatus is a complex mixture of lipids and proteins. In the present work we describe multiscale molecular dynamics simulations of transmembrane protein domains in model membranes that represent the in vivo Golgi environment. The transmembrane domain of glycosyltransferases is required for their correct sorting within the Golgi apparatus. The hydrophobic thickness and oligomerization state of the transmembrane domains have been proposed to mediate this sorting. Fukutin, is a putative Golgi glycosyltransferase implicated in muscular dystrophy.We employ atomistic and coarse-grained molecular dynamics simulations to investigate the stability and membrane interactions of the fukutin transmembrane domain, using various models of the membrane. Our atomistic simulations reveal that the fukutin transmembrane domain can exist as a stable α helix irrespective of the headgroup charge, fatty acid saturation or hydrophobic thickness of the lipid bilayer. Coarse-grained simulations reveal that the tilt angle of the fukutin transmembrane domain is highly variable and dependent upon its local environment; both the hydrophobic thickness and the headgroup charge of the lipid bilayer can alter the tilt angle of the protein. Lastly, we study the dynamics of the fukutin transmembrane domain in a mixed lipid bilayer whose composition closely mimics the complex lipid headgroup composition of the Golgi apparatus.