Jones C E, Busch H, Olson M O
Biochim Biophys Acta. 1981 Jan 30;667(1):209-12. doi: 10.1016/0005-2795(81)90081-7.
The sites of phosphorylation in protein B23, a silver-staining preribosomal ribonucleoprotein particle protein, were analyzed by tryptic peptide mapping. Three 32P peptides were found using in vitro labeling of nucleoli. An additional unlabeled phosphopeptide was identified by amino acid analysis. The sequence of the latter was Asp-Thr(P)-Pro-Ala-Lys. These results suggest that protein B23 contains one class of site labeled rapidly in vitro and another type of site phosphorylated only in vivo.
通过胰蛋白酶肽图谱分析了银染前核糖体核糖核蛋白颗粒蛋白B23中的磷酸化位点。利用核仁的体外标记发现了三种32P肽。通过氨基酸分析鉴定出一种额外的未标记磷酸肽。后者的序列为天冬氨酸-苏氨酸（磷酸化）-脯氨酸-丙氨酸-赖氨酸。这些结果表明，蛋白B23含有一类在体外快速标记的位点和另一类仅在体内磷酸化的位点。
