Carbohydrate-Binding Proteins in the Leech: I. Isolation and Characterization of Lactose-Binding Proteins

Authors

  • Robert N. Cole,

    1. Department of Physiology, Michigan State University, East Lansing, Michigan, U.S.A.
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    • The present address of Dr. R. N. Cole is Department of Biochemistry and Molecular Genetics, University of Alabama, Schools of Medicine and Dentistry, 404 Basic Health Sciences Building, Birmingham, AL 35294, U.S.A.

  • Birgit Zipser

    Corresponding author
    1. Department of Physiology, Michigan State University, East Lansing, Michigan, U.S.A.
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Address correspondence and reprint requests to Dr. B. Zipser at Department of Physiology, Michigan State University, 111 Giltner Hall, East Lansing, MI 48824, U.S.A.

Abstract

Abstract: Three lactose-binding proteins with apparent molecular masses of 16, 35, and 63 kDa [leech lectin 16, 35, and 63 (LL16, LL35, and LL63, respectively)] were isolated from leech membranes. Polyclonal antibodies raised against LL35 cross-reacted with LL16 and LL63, indicating that all three lectins were immunologically related. These leech lectins, however, can be subdivided into two groups based on their tissue distributions and binding affinities for galactose derivatives. LL16 and LL35 are endogenous to the leech's CNS, whereas LL63 is only present in peripheral organs. LL16 and LL35, found in the CNS, bind both the α and β anomers of methylgalactose, whereas the peripheral lectin LL63 binds only the β form. LL35 and LL63 also differ in their binding affinities for galactosamine and N-acetylgalactosamine. The binding activity of LL35 was calcium independent and active over a wide pH range. Triton X-100 and 2-mercaptoethanol were necessary to recover LL35 binding activity during extraction. These characteristics strongly suggest that LL35 is another member of the calcium-independent galactose/lactose-specific lectins previously described in vertebrates and recently demonstrated in sponges and nematodes. Because a single leech expresses up to 100 µg of LL35, this leech lectin is readily amenable to structural and functional analysis.

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