title: Protein SRP54 of human signal recognition particle: cloning, expression, and comparative analysis of functional sites.
abstract: Signal recognition particle (SRP) plays a critical role in the targeting of secretory proteins to cellular membranes. An essential component of SRP is the protein SRP54, which interacts not only with the nascent signal peptide, but also with the SRP RNA. To understand better how protein targeting occurs in the human system, the human SRP54 gene was cloned, sequenced, and the protein was expressed in bacteria and insect cells. Recombinant SRP54 was purified from both sources. The protein bound to SRP RNA in the presence of protein SRP19, and associated with the signal peptide of in vitro translated pre-prolactin. Comparative sequence analysis of human SRP54 with homologs from all three phylogenetic domains was combined with high-stringency protein secondary structure prediction. A conserved RNA-binding loop was predicted in the largely helical M-domain of SRP54. Contrary to general belief, the unusually high number of methionine residues clustered outside the predicted helices, thus indicating a mechanism of signal peptide recognition that may involve methionine-rich loops.
authors.affiliation: Department of Molecular Biology, University of Texas Health Science Center at Tyler 75710, USA.
authors.forename: K
authors.initials: K
authors.lastname: Gowda
authors.forename: S D
authors.initials: SD
authors.lastname: Black
authors.forename: I
authors.initials: I
authors.lastname: Moeller
authors.forename: Y
authors.initials: Y
authors.lastname: Sakakibara
authors.forename: M C
authors.initials: MC
authors.lastname: Liu
authors.forename: C
authors.initials: C
authors.lastname: Zwieb
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D003001:Cloning, Molecular; D004926:Escherichia coli; D015870:Gene Expression; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012313:RNA / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D018271:Signal Recognition Particle / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D018411:Spodoptera
chemical_list: D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D018271:Signal Recognition Particle; D012313:RNA