Polysaccharide Recognition by Surfactant Protein D:  Novel Interactions of a C-Type Lectin with Nonterminal Glucosyl Residues

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Allen, Martin
Laederach, Alain
Mason, Robert
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Chemical and Biological Engineering

The function of the Department of Chemical and Biological Engineering has been to prepare students for the study and application of chemistry in industry. This focus has included preparation for employment in various industries as well as the development, design, and operation of equipment and processes within industry.Through the CBE Department, Iowa State University is nationally recognized for its initiatives in bioinformatics, biomaterials, bioproducts, metabolic/tissue engineering, multiphase computational fluid dynamics, advanced polymeric materials and nanostructured materials.

The Department of Chemical Engineering was founded in 1913 under the Department of Physics and Illuminating Engineering. From 1915 to 1931 it was jointly administered by the Divisions of Industrial Science and Engineering, and from 1931 onward it has been under the Division/College of Engineering. In 1928 it merged with Mining Engineering, and from 1973–1979 it merged with Nuclear Engineering. It became Chemical and Biological Engineering in 2005.

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1913 - present

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  • Department of Chemical Engineering (1913–1928)
  • Department of Chemical and Mining Engineering (1928–1957)
  • Department of Chemical Engineering (1957–1973, 1979–2005)
    • Department of Chemical and Biological Engineering (2005–present)

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Surfactant protein D (SP-D), a C-type lectin, is an important pulmonary host defense molecule. Carbohydrate binding is critical to its host defense properties, but the precise polysaccharide structures recognized by the protein are unknown. SP-D binding toAspergillus fumigatus is strongly inhibited by a soluble β-(1→6)-linked but not by a soluble β-(1→3)-linked glucosyl homopolysaccharide (pustulan and laminarin, respectively), suggesting that SP-D recognizes only certain polysaccharide configurations, likely through differential binding to nonterminal glucosyl residues. In this study we have computationally docked α/β-d-glucopyranose and α/β-(1→2)-, α/β-(1→3)-, α/β-(1→4)-, and α/β-(1→6)-linked glucosyl trisaccharides into the SP-D carbohydrate recognition domain. As with the mannose-binding proteins, we found significant hydrogen bonding between the protein and the vicinal, equatorial OH groups at the 3 and 4 positions on the sugar ring. Our docking studies predict that α/β-(1→2)-, α-(1→4)-, and α/β-(1→6)-linked but not α/β-(1→3)-linked glucosyl trisaccharides can be bound by their internal glucosyl residues and that binding also occurs through interactions of the protein with the 2- and 3-equatorial OH groups on the glucosyl ring. By using various soluble glucosyl homopolysaccharides as inhibitors of SP-D carbohydrate binding, we confirmed the interactions predicted by our modeling studies. Given the sequence and structural similarity between SP-D and other C-type lectins, many of the predicted interactions should be applicable to this protein family.


This work was supported by grants from NIH (HL-29891) and EPA (R825702). M.J.A. was funded by Great West Life Assurance and Andrew Goodman Fellowships at the National Jewish Medical and Research Center, and A.L. was supported by National Science Foundation IGERT Program Award 9972653.

Posted with permission from Biochemistry, 40 (2001): 7789–7798, doi:10.1021/bi002901q. Copyright 2001 American Chemical Society.

Mon Jan 01 00:00:00 UTC 2001