Furuta K, Ichikawa A, Nakayama K, Tanaka S
Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan.
Inflamm Res. 2006 May;55(5):185-91. doi: 10.1007/s00011-006-0069-x.
We previously demonstrated that, when expressed in COS-7 cells, L-histidine decarboxylase (HDC), which has neither an amino terminal signal sequence nor a hydrophobic membrane anchor, was localized in the endoplasmic reticulum (ER), although its orientation in the membrane remains to be clarified.
METHODS & RESULTS: Protease digestion and immunofluorescence analyses of the cells, of which plasma membrane was selectively permeabilized, revealed that the amino terminal 50-kDa portion of HDC is hardly accessible to proteases and antibodies added exogenously from the cytosolic side. Green fluorescent protein fused with the carboxyl terminal 20-kDa region of HDC at its carboxyl terminus exhibited the same characteristics as native HDC.
These results indicate that HDC is tightly associated with the ER membrane with its carboxyl terminal region exposed on the cytosolic side.
我们之前证明，当在COS-7细胞中表达时，L-组氨酸脱羧酶（HDC）既没有氨基末端信号序列，也没有疏水膜锚定结构，尽管其在膜中的取向仍有待阐明，但它定位于内质网（ER）。
对质膜被选择性通透的细胞进行蛋白酶消化和免疫荧光分析，结果显示，从胞质侧添加的蛋白酶和抗体很难接触到HDC氨基末端50 kDa的部分。在其羧基末端与HDC羧基末端20 kDa区域融合的绿色荧光蛋白表现出与天然HDC相同的特征。
这些结果表明，HDC与内质网膜紧密结合，其羧基末端区域暴露在胞质侧。
