Guanine nucleotides modulate the ligand binding properties of cell surface folate receptors in Dictyostelium discoideum

FEBS Letters

De Wit, René J.W.¹  Bulgakov, Roman¹ 

[1] Cell Biology and Morphogenesis Unit, Zoological Laboratory, University of Leiden, Kaiserstraat 63, NL-2311 GP Leiden, The Netherlands

关键词: Folate receptor;    Guanine nucleotide;    G-protein;    Dictyostelium discoideum;   

DOI  :  10.1016/0014-5793(85)80530-5

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Dictyostelium discoideum cells show 2 distinct classes of cell surface binding sites for folates. One type is non-specific, i.e., binds folic acid (FA), 2-deaminofolic acid (DAFA), and methotrexate (MTX) with similar affinity (K _0.5 ⋍ 140 nM). Scatchard analysis of this non-specific binding type suggests either heterogeneity or negative cooperativity. Isolated D. discoideum membranes show similar binding characteristics. Guanine nucleotides changed the binding levels of [³H]MTX. In the presence of 0.1 mM GTP, the number of binding sites remains unchanged, while the affinity decreases. GDP and guanylyl imidodiphosphate (GPPNP) are required at about 20-fold higher concentration than GTP, which elicits a half-maximal effect at 15μM. Other guanine and adenine nucleotides are ineffective up to 1 mM. These results suggests that the non-specific cell surface receptor for folic acid interacts with a guanine nucleotide regulatory (G-) protein.

【 授权许可】

Unknown