TY  - JOUR
A1  - Banerjee, Pallavi
A1  - Lipowsky, Reinhard
A1  - Santer, Mark
T1  - Coarse-grained molecular model for the Glycosylphosphatidylinositol anchor with and without protein
JF  - Journal of Chemical Theory and Computation
N2  - Glycosylphosphatidylinositol (GPI) anchors are a unique class of complex glycolipids that anchor a great variety of proteins to the extracellular leaflet of plasma membranes of eukaryotic cells. These anchors can exist either with or without an attached protein called GPI-anchored protein (GPI-AP) both in vitro and in vivo. Although GPIs are known to participate in a broad range of cellular functions, it is to a large extent unknown how these are related to GPI structure and composition. Their conformational flexibility and microheterogeneity make it difficult to study them experimentally. Simplified atomistic models are amenable to all-atom computer simulations in small lipid bilayer patches but not suitable for studying their partitioning and trafficking in complex and heterogeneous membranes. Here, we present a coarse-grained model of the GPI anchor constructed with a modified version of the MARTINI force field that is suited for modeling carbohydrates, proteins, and lipids in an aqueous environment using MARTINI's polarizable water. The nonbonded interactions for sugars were reparametrized by calculating their partitioning free energies between polar and apolar phases. In addition, sugar-sugar interactions were optimized by adjusting the second virial coefficients of osmotic pressures for solutions of glucose, sucrose, and trehalose to match with experimental data. With respect to the conformational dynamics of GPI-anchored green fluorescent protein, the accessible time scales are now at least an order of magnitude larger than for the all-atom system. This is particularly important for fine-tuning the mutual interactions of lipids, carbohydrates, and amino acids when comparing to experimental results. We discuss the prospective use of the coarse-grained GPI model for studying protein-sorting and trafficking in membrane models.
KW  - Martini force-field
KW  - osmotic-pressure
KW  - potential-functions
KW  - aqueous-solution
KW  - dynamics
KW  - coefficient
KW  - simulation
KW  - trypanosoma
KW  - transition
KW  - parameters
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jctc.0c00056
SN  - 1549-9626
SN  - 1549-9618
VL  - 16
IS  - 6
PB  - ACS Publications
CY  - Washington DC
ER  -