Structure and biosynthesis of the signal-sequence receptor.
The signal-sequence receptor (SSR) has previously been shown to be a component of the environment which nascent polypeptides meet on passage through the endoplasmic reticulum (ER) membrane. We report here on the primary structure of the SSR as deduced from cDNA clones and from direct protein sequencing. The glycoprotein is synthesized with a cleavable amino-terminal signal sequence and contains only one classical membrane-spanning segment. Its insertion into the ER membrane during biosynthesis depends on the function of the signal-recognition particle. SSR shows a remarkable charge distribution with the amino terminus being highly negatively charged, and the cytoplasmic carboxyl terminus positively charged. The SSR can be phosphorylated in its cytoplasmic tail both in intact cells and in a cell-free system, suggesting a regulation of its function. The localization of the protein in the ER membrane was confirmed by immunofluorescence microscopy.
Prehn
S
S
Institut für Biochemie, Humboldt-Universität, Berlin, German Democratic Republic.
Herz
J
J
Hartmann
E
E
Kurzchalia
T V
TV
Frank
R
R
Roemisch
K
K
Dobberstein
B
B
Rapoport
T A
TA
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000032:analysis; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D008861:Microsomes / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000032:analysis; D010766:Phosphorylation; D011487:Protein Conformation; D011956:Receptors, Cell Surface / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D011994:Recombinant Proteins / Q000096:biosynthesis*; D015398:Signal Transduction; D014158:Transcription, Genetic; D014162:Transfection
D000596:Amino Acids; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D011994:Recombinant Proteins; C036318:signal peptide receptor; D004247:DNA