| Modification Notes |
In mammalian cells, protein translocation across the endoplasmic reticulum (ER) membrane is almost exclusively co-translational (1). This transport depends on the Sec61 complex, which is homologous to the yeast Sec61p complex and has been identified in mammals as a ribosome-bound pore-forming membrane protein complex (1,2). The Sec61 complex associates with two ubiquitous ER membrane proteins Sec62 (also designated human translocation protein 1 or HTP1) and Sec63 (1-3). The Sec61 complex forms the hydrophilic pore in the membrane through which the nascent polypeptide is translocated (4-7). Sec61p seems to be the evolutionary conserved component since homologues of Sec61p have been found both in bacteria and mammals (1,2). Sec62 is expressed in various human tissues such as the heart, brain, placenta, liver and pancreas (2). |