Integral plasma membrane proteins are also synthesized by ribosomes on the RER, but become inserted in the rough endoplasmic reticulum membrane rather than transported into the lumen. In During transport to the Golgi and then to the cell surface these proteins stay anchored  in the membrane,  the last vesicles  that  fuse with the plasma membrane then becoming latest plasma membrane that is given in the below figure. Note that, after insertion

          Figure: A simplified version of the signal hypothesis