Steinert P M, Wantz M L, Idler W W
Biochemistry. 1982 Jan 5;21(1):177-83. doi: 10.1021/bi00530a030.
Purified subunits of intermediate filaments obtained from a variety of tissues and cell types contain O-phosphoserine and, in some cases, smaller amounts of O-phosphothreonine. The O-phosphoserine content was estimated by reaction of performic acid oxidized subunits with methylamine in NaOH. Decamin of BHK-21 and CHO fibroblasts contained about 1 mol/mol. Avian and mammalian desmin consists of two subunits, an acidic (alpha) subunit which contained 2 mol/mol and a more basic (beta) nonphosphorylated subunit. The principal (Mr approximately 60 000) subunit of squid brain neurofilaments contained 5 mol/mol. Most mouse and bovine keratin subunits contained 3--6 mol/mol, although certain bovine subunits of higher molecular weight contained none. The O-phosphoserine contents of keratin subunits purified from the viable and stratum corneum layers were the same. The O-phosphoserine was located in non-alpha-helical regions of the subunits which presumably project out from the alpha-helical wall of the intermediate filaments. Most subunits could be partially dephosphorylated in vitro with alkaline phosphatase. It was found that the capacity of such partially dephosphorylated subunits for assembly into native-type filaments in vitro was independent of their phosphate content.
从多种组织和细胞类型中获得的中间丝纯化亚基含有O-磷酸丝氨酸，在某些情况下，还含有少量的O-磷酸苏氨酸。通过在NaOH中用甲胺处理过甲酸氧化的亚基来估计O-磷酸丝氨酸的含量。BHK-21和CHO成纤维细胞的脱氨基产物约含1摩尔/摩尔。鸟类和哺乳动物的结蛋白由两个亚基组成，一个酸性（α）亚基含2摩尔/摩尔，一个碱性更强的（β）非磷酸化亚基。鱿鱼脑神经丝的主要（分子量约为60000）亚基含5摩尔/摩尔。大多数小鼠和牛的角蛋白亚基含3 - 6摩尔/摩尔，不过某些分子量较高的牛亚基不含O-磷酸丝氨酸。从活层和角质层纯化的角蛋白亚基的O-磷酸丝氨酸含量相同。O-磷酸丝氨酸位于亚基的非α螺旋区域，这些区域大概从中间丝的α螺旋壁伸出。大多数亚基在体外能用碱性磷酸酶进行部分去磷酸化。发现这种部分去磷酸化的亚基在体外组装成天然型细丝的能力与其磷酸盐含量无关。
