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Structure of a tetrameric galectin from Cinachyrella sp. (ball sponge)
Douglas M Freymann1, Yuka Nakamura, Pamela J Focia
1Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA. freymann@northwestern.edu
Acta Crystallographica. Section D, Biological Crystallography
|September 6, 2012
Summary
Marine sponge galectins, like CchG-1, bind to N-acetyllactosamine and modulate glutamate receptors. Its novel tetrameric structure, stabilized by disulfide bonds, offers insights into receptor interactions.
Area of Science:
- Biochemistry
- Structural Biology
- Neuroscience
Background:
- Galectins are proteins binding N-acetyllactosamine, crucial in immunity and cancer metastasis.
- Marine sponges contain galectins with potential roles in modulating mammalian systems.
- Ionotropic glutamate receptors are vital for neurotransmission and implicated in neurological disorders.
Purpose of the Study:
- To elucidate the structural basis of galectin CchG-1's interaction with ionotropic glutamate receptors.
- To characterize the novel quaternary structure of a marine sponge galectin.
Main Methods:
- X-ray crystallography at 2.1 Å resolution.
- Bioactivity screening of marine sponge extracts.
- Structural analysis of galectin CchG-1.
Main Results:
- The X-ray structure of galectin CchG-1 revealed a novel tetrameric 'donut' arrangement.
- This structure is stabilized by the packing of vicinal disulfide bonds.
- The protomer shows similarity to mammalian galectins, but the tetramer is unique.
- The structure suggests a model for interaction with ionotropic glutamate receptors.
Conclusions:
- Galectin CchG-1 possesses a unique tetrameric structure distinct from mammalian galectins.
- Disulfide bond packing is critical for stabilizing the toroidal structure.
- The structural findings provide a mechanistic basis for galectin CchG-1's modulation of glutamate receptors.
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