ADP-RIBOSYLATION CYCLES

单ADP核糖基化是一种蛋白质翻译后修饰， 其中ADP-核糖通过氨基转移从NAD转移到蛋白质底物， 酸特异性ADP-核糖基转移酶。 修改可以逆转 通过ADP-核糖基精氨酸水解酶将ADP-核糖加合物 proteins. 一种arbinine特异性单ADP核糖基转移酶定位于 分化的小鼠骨骼肌细胞表面，锚定在 膜通过糖基磷脂酰肌醇尾巴。 孵育后 用[腺苷酸-32 P]NAD和十二烷基钠分析完整细胞 硫酸盐-聚丙烯酰胺凝胶电泳（SDS-PAGE），97-kDa [32 P]ADP- 在还原条件下观察到核糖基化蛋白， 在非还原条件下形成络合物。 ADP-核糖基化蛋白是 在层粘连蛋白亲和柱上纯化。 根据它的N端序列 （FNLDVMGAIRKEGEPGSLFGF）和部分内部序列 （GLMRSEELSFVAGAP），经鉴定为整合素 阿尔法7。 在部分胰蛋白酶消化后，39-kDa/79-kDa 产生放射性标记片段（还原/非还原SDS-PAGE）， 将ADP-核糖基化位点缩小到39-kDa片段， 整合素α 7的胞外结构域。 最优条件下的标记 条件为至少0.4mol ADP-核糖/mol整联蛋白α 7。 ADP-核糖基转移酶和整合素α 7的选择性表达 在心肌和骨骼肌中， 明显特异性ADP核糖基化，与调节一致 这些蛋白质之间的联系。 ADP-核糖基化可以调节 整合素受体信号传导，并可能在 细胞外基质对肌肉细胞功能的调节。

Mono-ADP-ribosylation is a posttranslational modification of proteins in which ADP-ribose is transferred from NAD to protein substrates by amino acid specific ADP-ribosyltransferases. The modification can be reversed by ADP-ribosylarginine hydrolase which removes the ADP-ribose adduct from proteins. An arbinine-specific mono-ADP-ribosyltransferase was localized to the surface of differentiated mouse skeletal muscle cells, anchored in the membrane via a glycosylphosphatidylinositol tail. Following incubation of intact cells with [adenylate-32P]NAD and analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), a 97-kDa [32P]ADP- ribosylated protein was observed under reducing conditions and a 140-kDa complex under nonreducing conditions. The ADP-ribosylated protein was purified on a laminin affinity column. Based on its N-terminal sequence (FNLDVMGAIRKEGEPGSLFGF) and a partial internal sequence (GLMRSEELSFVAGAP), the modified protein was identified as integrin alpha7. Following partial tryptic digestion, a 39-kDa/79-kDa radiolabeled fragment was produced (reduced/nonreduced SDS-PAGE), narrowing the ADP-ribosylation site to a 39-kDa segment in the extracellular domain of integrin alpha7. Labeling under optimal conditions was at least 0.4 mol of ADP-ribose/mol of integrin alpha7. Selective expression of both ADP-ribosyltransferase and integrin alpha7 in cardiac and skeletal muscle, similar developmental appearance and the apparently specific ADP-ribosylation, are consistent with a regulatory association between these proteins. ADP-ribosylation may modulate integrin receptor signaling and could play a significant role in the regulation of muscle cell function by the extracellular matrix.