title: Identification of an RNA-binding domain in human SRP72.
abstract: The signal recognition particle (SRP) is a ribonucleoprotein complex that plays a crucial role during the delivery of secretory proteins from the ribosome to the cell membrane. Among the six proteins of the eukaryotic SRP, the 72 kDa protein (SRP72) is the largest and least characterized. Polypeptides corresponding to various regions of the entire human SRP72 sequence were expressed in Escherichia coli, purified, and partially proteolyzed. Human SRP RNA bound with high affinity to a 63 amino acid residue region near the C terminus of SRP72. Mild treatment of the fragment with chymotrypsin abolished its RNA-binding activity. A conserved sequence with the consensus PDPXRWLPXXER was identified within a 56 amino acid residue RNA-binding domain. Sucrose gradient centrifugation and filter-binding analysis using mutant SRP RNAs showed that SRP72 bound to the moderately conserved portion of SRP RNA helix 5. Nine tetratricopeptide-like repeats (TPRs) poised to interact with other SRP or ribosomal proteins were predicted in the NH2-terminal region. These identifications assign two important functions to a large portion of SRP72 and demonstrate the RNA-binding capacity of the protein.
authors.affiliation: Department of Molecular Biology, The University of Texas Health Science Center at Tyler, 11937 US Highway 271, Tyler, TX 75708-3154, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Iakhiaeva
authors.forename: Jiaming
authors.initials: J
authors.lastname: Yin
authors.forename: Christian
authors.initials: C
authors.lastname: Zwieb
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D020029:Base Pairing; D001483:Base Sequence; D001665:Binding Sites; D015870:Gene Expression; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012313:RNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018271:Signal Recognition Particle / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; C503636:SRP72 protein, human; D018271:Signal Recognition Particle; D012313:RNA