Structural basis of flagellar motility regulation by the MogR repressor and the GmaR antirepressor in <i>Listeria monocytogenes</i>
So Yeon Cho, Hye-Won Na, Han Byeol Oh, Yun Mi Kwak, Wan Seok Song, Sun Cheol Park, Wook-Jong Jeon, Hongbaek Cho, Byung‐Chul Oh, Jeongho Park, Seung Goo Kang, Geun‐Shik Lee, Sung‐il Yoon
Abstract
The pathogenic Listeria monocytogenes bacterium produces the flagellum as a locomotive organelle at or below 30°C outside the host, but it halts flagellar expression at 37°C inside the human host to evade the flagellum-induced immune response. Listeria monocytogenes GmaR is a thermosensor protein that coordinates flagellar expression by binding the master transcriptional repressor of flagellar genes (MogR) in a temperature-responsive manner. To understand the regulatory mechanism whereby GmaR exerts the antirepression activity on flagellar expression, we performed structural and mutational analyses of the GmaR-MogR system. At or below 30°C, GmaR exists as a functional monomer and forms a circularly enclosed multidomain structure via an interdomain interaction. GmaR in this conformation recognizes MogR using the C-terminal antirepressor domain in a unique dual binding mode and mediates the antirepressor function through direct competition and spatial restraint mechanisms. Surprisingly, at 37°C, GmaR rapidly forms autologous aggregates that are deficient in MogR neutralization capabilities.