Integral membrane proteins are found within the plasma membrane and span the whole length across. The inside of the membrane is very hydrophobic due to the long carbon chains. Extensive hydrophobic interactions between the protein side chain and the lipid tails will help anchor the protein in the membrane.
I was thinking signal sequence on the N-terminal end that would direct the protein into the RER to be then implanted into the plasma membrane. I guess transmembrane region is the better more specific answer?