%0 Journal Article
%A High, Stephen
%A Martoglio, Bruno
%A Görlich, Dirk
%A Andersen, Soren S. L.
%A Ashford, Anthony J.
%A Giner, Angelika
%A Hartmann, Enno
%A Prehn, Siegfried
%A Rapoport, Tom A.
%A Dobberstein, Bernhard
%A Brunner, Josef
%D 1993
%F heidok:8569
%J The Journal of Biological Chemistry
%N 35
%P 26746-2671
%R 10.11588/heidok.00008569
%T Site-specific Photocross-linking Reveals That SecGlp and TRAM Contact Different Regions of a Membrane-inserted Signal Sequence
%U https://archiv.ub.uni-heidelberg.de/volltextserver/8569/
%V 268
%X A chemically charged amber suppressor tRNA was used to introduce the photoactivatable amino acid (Tmd)Phe at a selected position within the signal sequence of the secretory protein preprolactin. This allowed the interactions of the NH -terminal, the central, and the COOH-terminal regions of the signal sequence to be investigated during insertion into the membrane of the endoplasmic reticulum (ER). We found that different regions of the nascent chains were photocross-linked to different ER proteins. The TRAM protein (translocating chain-associating membrane protein) contacts the NHz-terminal region of the signal sequence while the mammalian Sec6lp contacts the hydrophobic core of the signal sequence and regions COOH-terminal of this. These results suggest that the ER translocation complex is composed of heterologous protein subunits which contadcti stinct regions of nascent polypeptides during their membrane insertion.