NMR structure and dynamics of the C-terminal domain of R-type lectin from the earthworm Lumbricus terrestris

Authors

  • Hikaru Hemmi,

    Corresponding author
    • National Food Research Institute, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
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  • Atsushi Kuno,

    1. Research Center for Medical Glycoscience, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
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  • Jun Hirabayashi

    1. Research Center for Medical Glycoscience, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
    Current affiliation:
    1. Research Center for Stem Cell Engineering, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
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Correspondence

H. Hemmi, National Food Research Institute, National Agriculture and Food Research Organization (NARO), 2-1-12 Kannondai, Tsukuba, 305-8642 Ibaraki, Japan

Fax: +81 298 387996

Tel: +81 298 388033

E-mail: hemmi@affrc.go.jp

Abstract

The C-terminal domain (Ch; C-half) of the R-type earthworm 29-kDa lectin (EW29), isolated from the earthworm Lumbricus terrestris, has two sugar-binding sites, in subdomains α and γ, and the protein uses the two sugar-binding sites for its function as a single domain-type haemagglutinin. Our previous NMR titration experiments showed that the α sugar-binding site is a high-affinity site and the γ sugar-binding site is a low-affinity site. However, it remains unclear why the α sugar-binding site of EW29Ch binds to lactose much more strongly because the crystal structure of lactose-bound EW29Ch showed that the interaction between the α sugar-binding site and lactose was almost same as that between the γ sugar-binding site and lactose. In the present study, we have determined the NMR structure of EW29Ch in the sugar-free state and performed 15N relaxation experiments for EW29Ch in both the sugar-free state and the lactose-bound states. The conformation of EW29Ch in the sugar-free state was similar to that of EW29Ch in complex with lactose. Conformational changes upon binding of lactose were observed only for the α sugar-binding site. By contrast, the 15N relaxation experiments revealed a conformational exchange at the α sugar-binding site in the sugar-free state, which was suppressed in the lactose-bound state. The conformational exchange phenomenon observed for the α sugar-binding site was not observed for the γ sugar-binding site. Differences in the conformational change and the backbone dynamics between subdomains α and γ may be associated with the difference of the sugar-binding modes between the two sugar-binding sites.

Database

Structural data for the NMR structure of EW29Ch in the sugar-free state have been deposited in the Protein Data Bank database under accession number 2RST.

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