Role of potentially charged transmembrane residues in targeting proteins for retention and degradation within the endoplasmic reticulum.
The selective breakdown of newly synthesized proteins retained within the endoplasmic reticulum (ER) is probably mediated by the specific recognition of structural features of protein substrates by components of a degradative system. Within the alpha chain of the multisubunit T-cell antigen receptor (TCR) complex, a transmembrane sequence containing two basic amino acid residues has been shown to act as a determinant for retention and rapid degradation in the ER. We now demonstrate that single basic or acidic amino acid residues can cause targeting for retention and degradation in the ER when placed within the transmembrane domain of an integral membrane protein normally destined for the cell surface. The effect of such potentially charged residues is dependent on their relative position within the transmembrane sequence and on the nature of the amino acid side chains. The phenotypic changes induced by potentially charged transmembrane residues occur without apparent alterations of the global folding or transmembrane topology of the mutant proteins. These observations test the hypothesis that potentially charged residues within transmembrane domains can provide the basis for a motif for ER degradation and explain the selective breakdown of some proteins retained within the ER.
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892.
J S
JS
Bonifacino
P
P
Cosson
N
N
Shah
R D
RD
Klausner
D000595:Amino Acid Sequence; D001693:Biological Transport, Active; D002460:Cell Line; D004563:Electrochemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006868:Hydrolysis; D008565:Membrane Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D011487:Protein Conformation; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism*; D015375:Receptors, Interleukin-2 / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; D015375:Receptors, Interleukin-2; D011993:Recombinant Fusion Proteins