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ABSTRACT: The invariant (Ii) chain is a membrane-spanning glycoprotein found intracellularly associated with class II major histocompatibility complex (MHC) molecules. Using hybridselected translation and the Ii-specific monoclonal antibody In-1, we have isolated a cDNA clone (pli-5) coding for most of the Ii chain. Sequence analysis of this clone reveals an open reading frame encoding 169 amino acid residues. The protein is rich in methionine and contains two potential N-glycosylation sites. No stretch of uncharged amino acid residues, characteristic for a membrane-spanning segment, is found close to the COOH-terminal end. There is one, however, close to the NH2-terminal end. As it is known that -20 amino acid residues of Ii chain are exposed on the cytoplasmic side, we conclude that the Ii chain spans the membrane exposing the NH2 terminus on the cytoplasmic side and the COOH terminus on the luminal side.
The EMBO Journal 05/1984; · 9.20 Impact Factor
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in: Nature 1989, 340: 478-482.
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in: The Journal of Cell Biology 1988, 106: 1813-1820.
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in: Cell 1986, 46: 1103-1112.
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in: Nucleic Acids Research 1988, 16: 3405-3414.
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in: The Journal of Biological Chemistry 1995, 270 (34): 19873-19878.
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in: Modulation of liver cell expression : proceedings of the 43. Falk Symposium, held during Basel Liver Week, Basel, October 14 and 15, 1986 / ed. by W. Reutter ... - Lancaster [u.a.] : MTP Press, S. 143-155.
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ABSTRACT: Bifunctional cross-linking reagents were used to probe the protein environment in the ER membrane of the signal sequence receptor (SSR), a 34-kD integral membrane glycoprotein (Wiedmann, M., T. V. Kurzchalia, E. Hartmarm, and T. A. Rapoport. 1987. Nature [Lond.]. 328:830-833). The proximity of several polypeptides was demonstrated. A 22-kD glycoprotein was identified tightly bound to the 34-kD SSR even after membrane solubilization. The 34-kD polypeptide, now termed otSSR, and the 22-kD polypeptide, the #SSR, represent a heterodimer. We report on the sequence of the/3SSR, its membrane topology, and on the mechanism of its integration into the membrane. Cross-linking also produced dimers of the a-subunit of the SSR indicating that oligomers of the SSR exist in the ER membrane. Various bifunctional cross-linking reagents were used to study the relation to ER membrane proteins of nascent chains of preprolactin and/3-1actamase at different stages of their translocation through the membrane. The predominant cross-linked products obtained in high yields contained the aSSR, indicating in conjunction with previous results that it is a major membrane protein in the neighborhood of translocating nascent chains of secretory proteins. The results support the existence of a translocon, a translocation complex involving the SSR, which constitutes the specific site of protein translocation across the ER membrane.
in: The Journal of Cell Biology 1990, 111 (6): 2283-2294.
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in: Methods in Enzymology 1987, 155: 416-433.
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ABSTRACT: In Escherichia coli, a signal recognition particle (SRP) has been identified which binds specifically to the signal sequence of presecretory proteins and which appears to be essential for efficient translocation of a subset of proteins. In this study we have investigated the function of E. coli FtsY which shares sequence similarity with the alpha-subunit of the eukaryotic SRP receptor ('docking protein') in the membrane of the endoplasmic reticulum. A strain was constructed which allows the conditional expression of FtsY. Depletion of FtsY is shown to cause the accumulation of the precursor form of beta-lactamase, OmpF and ribose binding protein in vivo, whereas the processing of various other presecretory proteins is unaffected. Furthermore, FtsY-depleted inverted cytoplasmic membrane vesicles are shown to be defective in the translocation of pre-beta-lactamase using an in vitro import assay. Subcellular localization studies revealed that FtsY is located in part at the cytoplasmic membrane with which it seems peripherally associated. These observations suggest that FtsY is the functional E. coli homolog of the mammalian SRP receptor.
in: The EMBO Journal 1995, 13 (10): 2289-2296.
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in: Cell 1990, 63: 591-600.
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Cold Spring Harbor Symposia on Quantitative Biology, Vol. LX: 41-45.
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Molecular Microbiology 11, 9-13.
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in: Molecular Biology Reports 1990, 14: 71-72.
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Nature 359, 741-743.
