Modeling Assembly of the Tata Pore Forming Complex using an Implicit Membrane Model

Many vital cellular processes, such as protein translocation, proton transport or molecular recognition, are mediated by self assembling membrane proteins. We have investigated the Twin-arginine translocase (TatA) complex, which forms transient pores through which proteins are translocated through the membrane. We postulated that complex formation is electrostatically driven by formation of salt bridges between amphiphilic transmembrane segments of the individual monomers and developed a structure-based model for this process[1]. We studied the formation of oligomers of different sizes by structure-based[2] MD simulations in combination with NMR constraints and a hydrophobic-slab implicit membrane model. Starting from isolated monomers, distributed far apart from each other, we observed the formation of stable TatA oligomers on the basis of the postulated interactions. The dimensions of the resulting TatA complex agreed well with experimental electron microscopy measure- ments[3] and the postulated interactions were confirmed by subsequent muta- tion studies