Importin-alpha-16 is a translocon-associated protein involved in sorting membrane proteins to the nuclear envelope.
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-alpha-16, a membrane-associated isoform of Spodoptera frugiperda importin-alpha that contains the C-terminal amino acid residues comprising armadillo helical-repeat domains 7-10. In the endoplasmic reticulum (ER) membrane, importin-alpha-16 is adjacent to the translocon protein Sec61alpha. Importin-alpha-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-alpha-16 discriminates between INM- and non-INM-directed proteins. Thus, it seems that during and after cotranslational membrane integration, importin-alpha-16 is involved in the trafficking of integral membrane proteins to the INM.
Saksena
Suraj
S
Department of Biochemistry and Biophysics, Texas A&M University, USA.
Summers
Max D
MD
Burks
Jared K
JK
Johnson
Arthur E
AE
Braunagel
Sharon C
SC
D000595:Amino Acid Sequence; D001483:Base Sequence; D017931:DNA Primers; D000939:Epitopes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009685:Nuclear Envelope / Q000378:metabolism*; D021381:Protein Transport; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D028901:alpha Karyopherins / Q000737:chemistry / Q000378:metabolism*
D017931:DNA Primers; D000939:Epitopes; D008565:Membrane Proteins; D028901:alpha Karyopherins