Three-dimensional solution structure of EM703 with potent promoting activity of monocyte-to-macrophage differentiation

EM703, which is an erythromycin derivative synthesized by our group, has a potent promoting activity of monocyte-to-macrophage differentiation in vitro. Its activity is approximately 300 times higher than that of erythromycin A (EM-A). In this study, we determined three-dimensional (3D) solution structures of EM703 and EM-A, and compared them using a superposition method, in order to investigate the 3D structure–activity relationship. We found a distinct difference between the 3D structures of these molecules, which might be an important factor in their divergent activities.