Differential contribution of M r 120 kDa rasGTPase‐activating protein and neurofibromatosis type 1 gene product during the transition from growth phase to arrested state in human fibroblasts accompanied by a unique rasGTPase‐activating active

[摘要]

Using octyl glucoside-solubilized cell extracts from human fibroblasts during growth phase to G₀/G₁ arrest state, we found that while the number of M _r, 120 kDa rasGTPase-activating protein (p120GAP) molecules per cell decreases to half its original levels, the amount of neurofibromatosis type 1 gene product (NF1, neurofibromin) remains constant during the transition. The contribution of pl20GAP to the total rasGTPase-activating (rasGA) activity in growing cells was found to be larger than that observed in arrested cells (84% vs 53%). On the other hand, NF1 contributes less than 15% of the total rasGA activity in either extract. These results indicate that the qualitative changes occur in the contributors to rasGA activity during transition. They also suggest that a unique rasGA activity exists in the arrested cells, which was obtained separatedly from both pl20GAP and NF1 by heparin-Sepharose column chromatography.

[学科分类] 生物化学/生物物理

[关键词] Ras;GTPase-activating protein;Neurofibromatosis type 1 gene product;Cell growth arrest;Human fibroblast;GAP;GTPase-activating protein;pl20GAP;GAP molecule with M r;120 kDa;NF1;neurofibromatosis type 1 gene product;NF1-GRD;NF1 GAP-related domain;DTT;dithiothreitol;TBST;Tris-buffered saline containing Tween 20