Our research is aimed at an integrated, atomistic understanding of molecular mechanisms of large protein complexes and assemblies by developing and combining novel technologies for high-resolution cryoEM and cryo-electron tomography with complementary computational and biophysical/biochemical methods.
HIV-1 capsid assembly, maturation, and interactions with host cells
Retroviruses, such as human immunodeficiency virus 1 (HIV-1), contain mature conical capsids that enclose the viral RNA genome, enzymes and accessory proteins. The assembly and stability of the viral capsid are critical to the viral replication life cycle. Structures of the building blocks of the capsid assembly were determined to atomic level, the mechanisms of capsid assembly and disassembly during a productive infection, however, remain unclear. Such information is essential for the development of therapeutic drugs that target viral capsid. More importantly, the surface of HIV-1 capsid serves a primary interaction interface between the virus and the host cell. Many host defense proteins have been identified to interact with the viral capsid and block HIV-1 infection. Yet, very little is known about their precise recognition and interactions, and thus mechanisms of inhibition. We are developing cutting-edge cryoEM technologies that bring unprecedented resolution and enable in situ structures of HIV-1 and in complex with host proteins, such as CypA, TRIM5α, TRIMCyp, CPSF6 and MxB, to decipher their underlining functional roles.
Bacterial chemotaxis sensory arrays
Bacteria use chemotaxis signaling pathways to monitor their environment and respond appropriately to change, which is crucial for colonization and infection for bacterial pathogens.The essential core signaling unit comprises transmembrane receptors, a histidine kinase CheA, and a coupling protein CheW. Remarkably, bacteria accomplish the extraordinary gain and cooperativity in chemotaxis signaling by arranging a few hundred core signaling units into higher order arrays localized at the cell pole. We developed a novel in vitro reconstitution system to generate signaling arrays, and succeeded in obtaining the first structure of the array using cryoET and sub-tomogram averaging. We aim to determine the precise molecular mechanisms of chemotaxis cooperative signaling using high-resolution cryoEM and cryoET in combination with site-directed mutagenesis and computational modeling. Our long-term goal is to develop plausible molecular models, at atomic resolution, for the entire signaling pathway by assembling structural “snapshots” of the signaling states.
CryoEM and cryoET technology development
Driven by biological questions and inspired by the bottlenecks we have to overcome, we devote significant efforts to the advancement of novel cryoEM methods and technologies. We are working on a wide spectrum of technical advances that will be essential to realize the promise of imaging cells and tissues at molecular resolutions, including correlative microscopy, cryo-FIB/SEM and high resolution sub-tomogram classification and averaging.