ER membrane Marker

[Martin Offterdinger]

Hi everyone,
I am looking for a marker protein for the ER membrane; it should be
expressed at reasonably high levels in all human cells and an antibody for
Westerns should be available. I thought about SRP receptor but I could not
find any antibody. I would like to use it as a control for a cell
fractionation experiment.
Thank you very much in advance,
martin