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Journal Article

Site-specific photocross-linking reveals that Sec61p and TRAM contact different regions of a membrane-inserted signal sequence.

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Görlich,  D.
Department of Cellular Logistics, MPI for biophysical chemistry, Max Planck Society;

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High, S., Martoglio, B., Görlich, D., Andersen, S. S., Ashford, A. J., Giner, A., et al. (1993). Site-specific photocross-linking reveals that Sec61p and TRAM contact different regions of a membrane-inserted signal sequence. The Journal of Biological Chemistry, 268(35), 26745-26751.


Cite as: https://hdl.handle.net/11858/00-001M-0000-0015-3BE2-9
Abstract
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 NH2-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 NH2-terminal region of the signal sequence while the mammalian Sec61p 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 contact distinct regions of nascent polypeptides during their membrane insertion.