We perform long-time-scale coarse-grained molecular dynamics simulations of the synthetic amphiphilic LS3 peptide interacting with a DPPC lipid bilayer. Our studies show that within several microseconds, the peptide assembles in a trans-membrane barrel-stave pore. The pore consists of six peptides and has an inner diameter of about 5.2 angstrom, which is comparable to earlier experimental and more detailed atomistic studies. Other structures such as three-, four-, and five-member bundles are also observed.