Assembly of the 68- and 72-kD proteins of signal recognition particle with 7S RNA.
Signal recognition particle (SRP), the cytoplasmic ribonucleoprotein particle that mediates the targeting of proteins to the ER, consists of a 7S RNA and six different proteins. The 68- (SRP68) and 72- (SRP72) kD proteins of SRP are bound to the 7S RNA of SRP as a heterodimeric complex (SRP68/72). Here we describe the primary structure of SRP72 and the assembly of SRP68, SRP72 and 7S RNA into a ribonucleoprotein particle. The amino acid sequence deduced from the cDNA of SRP72 reveals a basic protein of 671 amino acids which shares no sequence similarity with any protein in the sequence data libraries. Assembly of SRP72 into a ribonucleoprotein particle required the presence of 7S RNA and SRP68. In contrast, SRP68 alone specifically bound to 7S RNA. SRP68 contacts the 7S RNA via its NH2-terminal half while COOH-terminal portions of SRP68 and SRP72 are in contact with each other in SRP. SRP68 thus serves as a link between 7S RNA and SRP72. As a large NH2-terminal domain of SRP72 is exposed on SRP it may be a site of contact to other molecules involved in the SRP cycle between the ribosome and the ER membrane.
European Molecular Biology Laboratory, Heidelberg, Germany.
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Lütcke
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Prehn
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AJ
Ashford
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Remus
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Frank
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Dobberstein
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D004285:Dogs; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D021382:Protein Sorting Signals / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000648:ultrastructure*; D015183:Restriction Mapping; D012261:Ribonucleoproteins / Q000648:ultrastructure*; D018271:Signal Recognition Particle; D013329:Structure-Activity Relationship
D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides; D010446:Peptide Fragments; D021382:Protein Sorting Signals; D012342:RNA, Small Nuclear; D012261:Ribonucleoproteins; D018271:Signal Recognition Particle; C503637:Srp72 protein, mouse; D004247:DNA