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Structure. 2016 Jun 7;24(6):956-64. doi: 10.1016/j.str.2016.04.003. Epub 2016 May 5.

The Structure of a Sugar Transporter of the Glucose EIIC Superfamily Provides Insight into the Elevator Mechanism of Membrane Transport.

Author information

1
Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA.
2
Department of Molecular Biosciences, Center for Computational Biology, The University of Kansas, Lawrence, KS 66047, USA.
3
Department of Chemistry, College of Staten Island, Staten Island, NY 10314, USA.
4
Division of Molecular Therapeutics, Department of Psychiatry, Center for Molecular Recognition, New York State Psychiatric Institute, Columbia University, New York, NY 10032, USA.
5
Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA. Electronic address: mzhou@bcm.edu.

Abstract

The phosphoenolpyruvate:carbohydrate phosphotransferase systems are found in bacteria, where they play central roles in sugar uptake and regulation of cellular uptake processes. Little is known about how the membrane-embedded components (EIICs) selectively mediate the passage of carbohydrates across the membrane. Here we report the functional characterization and 2.55-Å resolution structure of a maltose transporter, bcMalT, belonging to the glucose superfamily of EIIC transporters. bcMalT crystallized in an outward-facing occluded conformation, in contrast to the structure of another glucose superfamily EIIC, bcChbC, which crystallized in an inward-facing occluded conformation. The structures differ in the position of a structurally conserved substrate-binding domain that is suggested to play a central role in sugar transport. In addition, molecular dynamics simulations suggest a potential pathway for substrate entry from the periplasm into the bcMalT substrate-binding site. These results provide a mechanistic framework for understanding substrate recognition and translocation for the glucose superfamily EIIC transporters.

PMID:
27161976
PMCID:
PMC4899283
DOI:
10.1016/j.str.2016.04.003
[Indexed for MEDLINE]
Free PMC Article

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