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

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

  • Biophysics
  • Biochemistry
  • Cell Biology

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