Nature Structural & Molecular Biology 13, 500 - 508 (2006)
Published online: 21 May 2006; | doi:10.1038/nsmb1098
Importin- -16 is a translocon-associated protein involved in sorting membrane proteins to the nuclear envelopeSuraj Saksena1, Max D Summers1, 2, 3, 4, Jared K Burks2, Arthur E Johnson1, 5, 6
& Sharon C Braunagel3, 41
Departments of Biochemistry and Biophysics, Texas A&M University, Texas 77843, USA. 2
Department of Biology, Texas A&M University, Texas 77843, USA. 3
Department of Entomology, Texas A&M University, Texas 77843, USA. 4
Texas Agricultural Experiment Station, Texas A&M University, Texas 77843, USA. 5
Department of Chemistry, Texas A&M University System Health Science Center, College Station, Texas 77843, USA. 6
Medical Biochemistry and Genetics, Texas A&M University System Health Science Center, College Station, Texas 77843, USA.
Correspondence should be addressed to Sharon C Braunagel s-brauna@tamu.edu A viral inner nuclear membrane–sorting motif sequence (INM-SM) was used to identify proteins that recognize integral membrane proteins destined for the INM. Herein we describe importin- -16, a membrane-associated isoform of Spodoptera frugiperda importin- that contains the C-terminal amino acid residues comprising armadillo helical-repeat domains 7–10. In the endoplasmic reticulum (ER) membrane, importin--16 is adjacent to the translocon protein Sec61. Importin--16 cross-links to the INM-SM sequence as it emerges from the ribosomal tunnel and remains adjacent to the INM-SM after INM-SM integration into the ER membrane and release from the translocon. Cross-linking results suggest that importin--16 discriminates between INM- and non–INM-directed proteins. Thus, it seems that during and after cotranslational membrane integration, importin--16 is involved in the trafficking of integral membrane proteins to the INM.
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