The phosphoenolpyruvate-dependent phosphotranferase system (PTS) is a multicomponent carbohydrate uptake system that is also involved in the regulation of metabolism, chemotaxis, and pathogenicity in bacteria. The PTS drives active transport of sugar by coupling the translocation of the ligand across the membrane with its concomitant covalent modification by phosphorylation to prevent efflux. The PTS has been the subject of extensive study for nearly half a century, but our understanding of the system has remained incomplete due to the lack of any structures for the integral membrane component EIIC responsible for the transport of the sugar across the inner membrane. The EIICs also confer specificity for a particular sugar to the PTS, and assist in the transfer of the phosphate from the cytoplasmic PTS protein EIIB to the sugar. We intend to address this gap in the mechanistic understanding of the PTS by combining structural and functional studies of ChbC, a member of the glucose EIIC superfamily that is specific for the uptake of N.N'- diacetylchitobiose. This sugar is produced by the breakdown of chitin, and as an important nutrient in the life cycle of pathogens such as Vibrio cholerae. To this end, we have solved the structure of a ChbC ortholog from Bacillus cereus (bcChbC), which has led us to propose hypotheses for how the transporter selectively binds sugar, translocates it across the membrane, and assists in coupling phosphorylation to transport. We will use this structure to understand the mechanism of EIIC function with three aims: (1) to determine the structural basis of bcChbC's substrate selectivity with binding and uptake assays, (2) to uncover the mechanism of phosphorylation by solving the structure of an bcChbC in complex with its partner EIIB, bcChbB, and (3) to reconstruct the conformational changes underlying the transport cycle by solving the structure of the outward- facing open state of bcChbC.
N,N'-diactelychitobiose, a degradation product of chitin, is a vital food source for many bacteria, including the cholera-causing pathogen Vibrio cholerae, which survives on the chitin in the shells of its microcrustacean hosts during its water-bourne phase. Because the uptake system for N,N'-diactelychitobiose is unique to bacteria, it is a potential target for disrupting the lifecycle of this devastating pathogen. Our studies of the ChbC transporter will help shed light on the mechanism of the N,N'-diactelychitobiose uptake system.
| Ren, Zhenning; Lee, Jumin; Moosa, Mahdi Muhammad et al. (2018) Structure of an EIIC sugar transporter trapped in an inward-facing conformation. Proc Natl Acad Sci U S A 115:5962-5967 |
| Lee, Jumin; Ren, Zhenning; Zhou, Ming et al. (2017) Molecular Simulation and Biochemical Studies Support an Elevator-type Transport Mechanism in EIIC. Biophys J 112:2249-2252 |
| McCoy, Jason G; Ren, Zhenning; Stanevich, Vitali et al. (2016) The Structure of a Sugar Transporter of the Glucose EIIC Superfamily Provides Insight into the Elevator Mechanism of Membrane Transport. Structure 24:956-64 |
| Bai, Yonghong; McCoy, Jason G; Levin, Elena J et al. (2015) X-ray structure of a mammalian stearoyl-CoA desaturase. Nature 524:252-6 |
| McCoy, Jason G; Levin, Elena J; Zhou, Ming (2015) Structural insight into the PTS sugar transporter EIIC. Biochim Biophys Acta 1850:577-85 |
| Levin, Elena J; Zhou, Ming (2014) Recent progress on the structure and function of the TrkH/KtrB ion channel. Curr Opin Struct Biol 27:95-101 |
| Zhou, Xiaoming; Levin, Elena J; Pan, Yaping et al. (2014) Structural basis of the alternating-access mechanism in a bile acid transporter. Nature 505:569-73 |
| Levin, Elena J; Zhou, Ming (2014) Structure of urea transporters. Subcell Biochem 73:65-78 |
| Huang, Hua; Levin, Elena J; Liu, Shian et al. (2014) Structure of a membrane-embedded prenyltransferase homologous to UBIAD1. PLoS Biol 12:e1001911 |
| Coudray, Nicolas; Valvo, Salvatore; Hu, Minghui et al. (2013) Inward-facing conformation of the zinc transporter YiiP revealed by cryoelectron microscopy. Proc Natl Acad Sci U S A 110:2140-5 |
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