Dataset Information

The sodium/galactose symporter crystal structure is a dynamic, not so occluded state.

ABSTRACT: The recent elucidation of the sodium/galactose symporter structure from the Vibrio parahaemolyticus bacterium, vSGLT, has revealed a similarity in the core architecture with transporters from different gene families, including the leucine transporter (LeuT). Even though several transporters sharing this core have been structurally determined over the past few years, vSGLT is the only one crystallized in the substrate-bound inward-facing conformation so far. In this study, we report the first insight into the dynamics and coordination of the galactose (Gal) and proposed Na+ ion in vSGLT using a series of molecular dynamics simulations with a total time of about 0.1 micros. Our study reveals new residues, not observed in the crystal structure, which closely interact with the Na(+) ion or the substrate for extended times, and shows that in the crystallized conformation, a Na+ ion placed at the site equivalent to Na2 in LeuT can escape into the intracellular (IC) space in the absence of external forces. We have identified the highly conserved Asp189 as a likely binding residue on the pathway of Na(+) into the IC cavity. The release of Gal, on the other hand, requires the rotation of the side chain of the inner hydrophobic gate, Tyr263, without a significant change in vSGLT backbone conformation. Our simulations further show that the crystal structure represents but one accessible binding pose of Gal and Na+ among an ensemble of microstates, and that the Gal undergoes versatile alternate interactions at the binding pocket.

SUBMITTER: Zomot E

PROVIDER: S-EPMC2938171 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

The sodium/galactose symporter crystal structure is a dynamic, not so occluded state.

Zomot Elia E Bahar Ivet I

Molecular bioSystems 20100331 6

The recent elucidation of the sodium/galactose symporter structure from the Vibrio parahaemolyticus bacterium, vSGLT, has revealed a similarity in the core architecture with transporters from different gene families, including the leucine transporter (LeuT). Even though several transporters sharing this core have been structurally determined over the past few years, vSGLT is the only one crystallized in the substrate-bound inward-facing conformation so far. In this study, we report the first ins ...[more]

PMID: 20358053

Similar Datasets

Project description:Background: The ability of thyroid follicular epithelial cells to accumulate iodide via the sodium/iodide symporter (NIS) is exploited to successfully treat most thyroid cancers, although a subset of patients lose functional NIS activity and become unresponsive to radioiodide therapy, with poor clinical outcome. Our knowledge of NIS regulation remains limited, however. While numerous membrane proteins are functionally regulated via dimerization, there is little definitive evidence of NIS dimerization, and whether this might impact upon radioiodide uptake and treatment success is entirely unknown. We hypothesized that NIS dimerizes and that dimerization is a prerequisite for iodide uptake. Methods: Coimmunoprecipitation, proximity ligation, and Förster resonance energy transfer (FRET) assays were used to assess NIS:NIS interaction. To identify residues involved in dimerization, a homology model of NIS structure was built based on the crystal structure of the dimeric bacterial protein vSGLT. Results: Abundant cellular NIS dimerization was confirmed in vitro via three discrete methodologies. FRET and proximity ligation assays demonstrated that while NIS can exist as a dimer at the plasma membrane (PM), it is also apparent in other cellular compartments. Homology modeling revealed one key potential site of dimeric interaction, with six residues <3Å apart. In particular, NIS residues Y242, T243, and Q471 were identified as critical to dimerization. Individual mutation of residues Y242 and T243 rendered NIS nonfunctional, while abrogation of Q471 did not impact radioiodide uptake. FRET data show that the putative dimerization interface can tolerate the loss of one, but not two, of these three clustered residues. Conclusions: We show for the first time that NIS dimerizes in vitro, and we identify the key residues via which this happens. We hypothesize that dimerization of NIS is critical to its trafficking to the PM and may therefore represent a new mechanism that would need to be considered in overcoming therapeutic failure in patients with thyroid cancer.

Dataset Information

The sodium/galactose symporter crystal structure is a dynamic, not so occluded state.

Publications

The sodium/galactose symporter crystal structure is a dynamic, not so occluded state.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets