The signal recognition particle receptor mediates the GTP-dependent displacement of SRP from the signal sequence of the nascent polypeptide.
The signal recognition particle (SRP)-mediated transport of proteins across mammalian endoplasmic reticulum requires GTP in a capacity distinct from polypeptide elongation. We defined the role of GTP by a molecular characterization of translocation intermediates that accumulate after incubation of SRP-ribosome complexes with microsomal membranes. SRP receptor-catalyzed displacement of SRP from ribosomes was GTP-dependent both with intact membranes and with the purified SRP receptor. GTP-specific binding was localized to the alpha subunit of the receptor by photoaffinity labeling and by probing nitrocellulose blots of the receptor with GTP. Analysis of the alpha subunit of the SRP receptor revealed amino acid sequences that are similar to guanine ribonucleotide binding site consensus sequence elements.
Connolly
T
T
Department of Biochemistry, University of Massachusetts Medical School, Worcester 01655.
Gilmore
R
R
D000345:Affinity Labels / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D004285:Dogs; D019286:Endopeptidase K; D006150:Guanine Nucleotides / Q000032:analysis; D006160:Guanosine Triphosphate / Q000378:metabolism / Q000502:physiology*; D007425:Intracellular Membranes / Q000032:analysis / Q000648:ultrastructure; D008861:Microsomes / Q000648:ultrastructure; D008969:Molecular Sequence Data; D010179:Pancreas / Q000648:ultrastructure; D021382:Protein Sorting Signals / Q000032:analysis* / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D011956:Receptors, Cell Surface / Q000378:metabolism / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D012261:Ribonucleoproteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000032:analysis / Q000378:metabolism; D012697:Serine Endopeptidases; D018271:Signal Recognition Particle; D013728:Terminator Regions, Genetic; D014178:Translocation, Genetic
D000345:Affinity Labels; D006150:Guanine Nucleotides; D021382:Protein Sorting Signals; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D012261:Ribonucleoproteins; D018271:Signal Recognition Particle; C036318:signal peptide receptor; D006160:Guanosine Triphosphate; D012697:Serine Endopeptidases; D019286:Endopeptidase K