Discoidin I-membrane interactions I. Discoidin I binds to two types of receptor on fixed Dictyostelium discoideum cells

James R. Bartles, William A. Frazier*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Under physiological buffer conditions (17 mM Pi, pH 6.3), the endogenous lectin of Dictyostelium discoideum, discoidin I, binds to two types of receptors on the surface of glutaraldehyde-fixed, wild-type (NC-4) D. discoideum cells. We have designated these two types of receptors the carbohydrate or C sites and the ionic or I sites. Binding to the C sites is saturable with respect to discoidin I and is inhibited by hapten sugars (such as N-acetyl-d-galactosamine), but not by increasing buffer ionic strength with NaCl or polyelectrolytes. The number of C sites increases about 4-fold during the first 8.5 h of suspension differentiation, reaching a capacity for about 2-104 discoidin I tetramers per cell. The binding activity of the C sites is reduced about 50% by sequential NaIO4 oxidation/NaBH4 reduction of the fixed cells, but it is not reduced by CHCl3-CH3OH extraction of the fixed cells. In marked contrast, binding to the I sites appears nonsaturable with respect to discoidin I, and it is inhibited by increasing buffer ionic strength with NaCl or polyelectrolytes (such as poly-l-glutamic acid or heparin), but not by hapten sugars. The I sites are present on both vegetative and differentiated fixed cells and can bind more than 106 discoidin I tetramers per cell. The binding activity of the I sites on fixed cells is not reduced by sequential NaIO4 oxidation/NaBH4 reduction, but is reduced 70 to 90% by CHCl3-CH3OH extraction. The data suggest that the I sites represent ionic lipids that bind discoidin I electrostatically.

Original languageEnglish (US)
Pages (from-to)121-128
Number of pages8
JournalBBA - Biomembranes
Volume687
Issue number2
DOIs
StatePublished - May 7 1982

Keywords

  • (D. discoideum)
  • Binding site
  • Discoidin I-membrane interaction
  • Kinetics
  • Membrane receptor

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology

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