The five N-terminal five transmembrane alpha-helices of peptidase_M48 family proteins including the CAAX prenyl proteases reside completely within the membrane of the endoplasmic reticulum.

1: Structure of the integral membrane protein CAAX protease Ste24p. Pryor EE Jr, Horanyi PS, Clark KM, Fedoriw N, Connelly SM, Koszelak-Rosenblum M, Zhu G, Malkowski MG, Wiener MC, Dumont ME; Science. 2013;339:1600-1604. PMID:23539602

2: The structural basis of ZMPSTE24-dependent laminopathies. Quigley A, Dong YY, Pike AC, Dong L, Shrestha L, Berridge G, Stansfeld PJ, Sansom MS, Edwards AM, Bountra C, von Delft F, Bullock AN, Burgess-Brown NA, Carpenter EP; Science. 2013;339:1604-1607. PMID:23539603