Trans-membrane translocation of proteins. The direct transfer model

As a start towards a deeper understanding of the transmembrane transport of proteins, the transfer of a nascent chain through the lipophilic core of a membrane is discussed from a physico-chemical point of view. Some simple considerations of the energetics of protein structure, together with experimental data on the transfer process, form the basis for a detailed and quantifiable model, accounting for the extrusion of secreted proteins as well as for the insertion of trans-membrane proteins.