GUANINE-NUCLEOTIDES MODULATE THE LIGAND-BINDING PROPERTIES OF CELL-SURFACE FOLATE RECEPTORS IN DICTYOSTELIUM-DISCOIDEUM
GUANINE-NUCLEOTIDES MODULATE THE LIGAND-BINDING PROPERTIES OF CELL-SURFACE FOLATE RECEPTORS IN DICTYOSTELIUM-DISCOIDEUM
复制标题
DOI：
10.1016/0014-5793(85)80530-5
复制
发表时间：
1985-01-01
期刊：
影响因子：
3.5
通讯作者：
BULGAKOV, R
中科院分区：
文献类型：
--
作者：
DEWIT, RJW;BULGAKOV, R
盘状骨鞘盘状细胞显示出两种不同类型的叶酸结合位点。一种是非特异性的，即结合叶酸（FA）， 2-脱氨叶酸（DAFA）和甲氨蝶呤（MTX）具有相似的亲和力（K0.5⋍140 nM）。Scatchard分析表明，这种非特异性结合类型要么具有异质性，要么具有负协同性。IsolatedD。盘状膜表现出类似的结合特性。鸟嘌呤核苷酸改变了[3H]MTX的结合水平。在0.1 mM GTP存在的情况下，结合位点数量保持不变，而亲和力降低。GPPNP （guanylyl imidodiphosphate， GPPNP）和GTP在15μM处的浓度是GTP的20倍。其他鸟嘌呤和腺嘌呤核苷酸在1毫米内无效。这些结果表明，叶酸的非特异性细胞表面受体与鸟嘌呤核苷酸调节（G-）蛋白相互作用。
Dictyostelium discoideumcells 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 (K0.5⋍ 140 nM). Scatchard analysis of this non-specific binding type suggests either heterogeneity or negative cooperativity. IsolatedD. discoideummembranes 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.