Membrane orientation of the precursor 74-kDa form of L-histidine decarboxylase.
OBJECTIVE
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.


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.


CONCLUSIONS
These results indicate that HDC is tightly associated with the ER membrane with its carboxyl terminal region exposed on the cytosolic side.
Furuta
K
K
Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan.
Ichikawa
A
A
Nakayama
K
K
Tanaka
S
S
D000818:Animals; D001426:Bacterial Proteins / Q000494:pharmacology; D019556:COS Cells; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D006640:Histidine Decarboxylase / Q000737:chemistry* / Q000378:metabolism; D007425:Intracellular Membranes / Q000201:enzymology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D013301:Streptolysins / Q000494:pharmacology
D001426:Bacterial Proteins; D013301:Streptolysins; C025964:streptolysin O; D007770:L-Lactate Dehydrogenase; D006640:Histidine Decarboxylase