Structural insight into the PTS sugar transporter EIIC

• Published in: Biochimica et biophysica acta Vol. 1850; no. 3; pp. 577 - 585
• Main Authors: McCoy, Jason G., Levin, Elena J., Zhou, Ming
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2015
• Subjects: Amino Acid Sequence; amino acid sequences; bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; binding sites; biophysics; carbohydrate binding; ChbC; crystal structure; Enzyme IIC; glucose; Glucose - chemistry; Glucose - metabolism; glutamic acid; histidine; Membrane protein; Membrane Transport Proteins - chemistry; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Models, Molecular; Molecular Sequence Data; Phosphorylation; Phosphotransferase system; Protein Binding; Protein Structure, Tertiary; sequence diversity; Sequence Homology, Amino Acid; Sugar transport; topology; Transporter; transporters; Enzyme IIC; Membrane protein; Transporter; ChbC; Phosphotransferase system; Sugar transport
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2014.03.013

The enzyme IIC (EIIC) component of the phosphotransferase system (PTS) is responsible for selectively transporting sugar molecules across the inner bacterial membrane. This is accomplished in parallel with phosphorylation of the sugar, which prevents efflux of the sugar back across the membrane. This process is a key part of an extensive signaling network that allows bacteria to efficiently utilize preferred carbohydrate sources. The goal of this review is to examine the current understanding of the structural features of the EIIC and how it mediates concentrative, selective sugar transport. The crystal structure of an N,N′-diacetylchitobiose transporter is used as a structural template for the glucose superfamily of PTS transporters. Comparison of protein sequences in context with the known EIIC structure suggests that members of the glucose superfamily of PTS transporters may exhibit variations in topology. Despite these differences, a conserved histidine and glutamate appear to have roles shared across the superfamily in sugar binding and phosphorylation. In the proposed transport model, a rigid body motion between two structural domains and movement of an intracellular loop provide the substrate binding site with alternating access, and reveal a surface required for interaction with the phosphotransfer protein responsible for catalysis. The structural and functional data discussed here give a preliminary understanding of how transport in EIIC is achieved. However, given the great sequence diversity between varying glucose-superfamily PTS transporters and lack of data on conformational changes needed for transport, additional structures of other members and conformations are still required. This article is part of a Special Issue entitled: Structural biochemistry and biophysics of membrane proteins. •We review structure/function in the glucose superfamily of PTS transporters.•bcChbC can be used as a structural template for other PTS subfamilies.•We propose mechanisms for both sugar phosphorylation and transport.