| 1990 |
SRP68 is a basic protein of 622 amino acids with a glycine-rich region near the amino terminus shared with certain RNA-binding proteins; it was cloned and sequenced from canine SRP. |
cDNA cloning and sequencing |
FEBS letters |
Medium |
1702390
|
| 1992 |
SRP68/72 heterodimer binds directly and specifically to SRP RNA with a Kd of ~7 nM; binding increases fluorescein anisotropy but does not alter emission intensity, and binding of SRP68/72 and SRP9/14 heterodimers to SRP RNA is noncooperative in the absence of SRP54 and SRP19. |
Fluorescence spectroscopy, equilibrium binding assays with purified SRP components |
Biochemistry |
High |
1377027
|
| 1993 |
SRP68 alone binds specifically to 7S RNA via its N-terminal half; SRP72 assembly into the ribonucleoprotein requires both 7S RNA and SRP68; the C-terminal portions of SRP68 and SRP72 contact each other; SRP68 thus serves as a physical link between 7S RNA and SRP72. |
In vitro reconstitution, domain mapping with deletion constructs, co-immunoprecipitation |
The Journal of cell biology |
High |
8388879
|
| 1994 |
Disruption of yeast SRP68 (Srp68p) gene causes slow cell growth and inefficient protein translocation across the ER membrane, phenotypically indistinguishable from loss of other SRP components; loss of Srp68p also reduces levels of scR1 RNA and other SRP proteins, indicating it is required for stable SRP expression. |
Gene disruption, genetic epistasis, translocation assays in Saccharomyces cerevisiae |
The EMBO journal |
High |
7925282
|
| 2000 |
GFP fusions of SRP68 localize to the nucleolus as well as the cytoplasm; SRP68 also accumulates at the ER, consistent with its affinity for the ER-bound SRP receptor; suggesting partial SRP assembly or another SRP68 activity occurs at the nucleolus. |
GFP transfection, live-cell fluorescence microscopy, immunofluorescence in rat fibroblasts |
Proceedings of the National Academy of Sciences of the United States of America |
High |
10618370
|
| 2006 |
The RNA-binding domain of human SRP68 maps to residues 52–252, and the SRP72-binding domain maps to ~94 amino acids near the C-terminus of SRP68; the SRP68-SRP72 interaction is salt-stable and engages ~150 amino acids from the N-terminal region of SRP72 (within predicted TPR-like motifs). |
Recombinant protein expression, proteolytic fragmentation, in vitro binding assays (pulldown, filter assay) |
Protein science |
High |
16672232
|
| 2006 |
SRP68/72 binding protects the SRP54 binding site (helix 8 asymmetric loop) from chemical modification, and together with SRP19 rearranges the 7SL RNA into an SRP54-binding-competent state; SRP68/72 brings the lower parts of helices 6 and 8 closer together as shown by hydroxyl radical footprinting and DMS modification. |
Chemical probing (ethylation interference, DMS modification), hydroxyl radical footprinting, enzymatic probing of SRP assembly intermediates |
Journal of molecular biology |
High |
17254600
|
| 2007 |
SRP68/72 contacts RNA residues throughout the large SRP domain including helix 5 (residues 222–231) and helix 8 (residues 176–191 and 202–214); SRP72 alone contacts mainly the 5ef region of helix 5; deleting helix 8 impairs SRP68/72 binding more than deleting helix 6. |
Systematic mutagenesis of SRP RNA helices, competitive double-filter binding assay with purified SRP68/72 and SRP72 fragment |
RNA biology |
High |
18347438
|
| 2008 |
SRP19 and SRP68/72 both bind directly and specifically to helices 6 and 8 of SRP RNA but on opposite faces and ends; their binding is moderately anti-cooperative, arising from stabilization of distinct conformations in the intervening RNA scaffold; SRP72 enhances SRP68 affinity for RNA via largely non-specific electrostatic interactions. |
Quantitative RNA-protein binding assays, SHAPE/chemical probing, anti-cooperativity analysis |
The Biochemical journal |
High |
18564060
|
| 2012 |
SRP68/72 heterodimer (but not intact SRP) binds histone H4 tail peptides in vitro and associates with chromatin in vivo; this binding is inhibited by PRMT5/PRMT1-mediated H4R3 methylation; both SRP68 and SRP72 activate transcription when tethered to a reporter, revealing a non-canonical chromatin/transcriptional regulatory function. |
Proteomic pulldown with histone peptides, ChIP, chromatin fractionation, transcription reporter assays, genome-wide occupancy analysis |
The Journal of biological chemistry |
High |
23048028
|
| 2014 |
Crystal structure of SRP68 RNA-binding domain (SRP68-RBD) alone and in complex with SRP RNA and SRP19 reveals SRP68-RBD is a tetratricopeptide-like module that binds the RNA three-way junction (helices 5, 6, 8), bends the RNA, and inserts an α-helical arginine-rich motif (ARM) into the major groove; the ARM opens the conserved 5f RNA loop, which contacts ribosomal RNA in ribosome-bound SRP. |
X-ray crystallography (crystal structures of apo SRP68-RBD and SRP68-RBD/SRP RNA/SRP19 complex), functional mutagenesis |
Science |
High |
24700861
|
| 2016 |
Crystal structure of SRP72-RBD bound to the SRP S domain (SRP RNA + SRP19 + SRP68) shows SRP72-RBD is a flexible peptide crawling along the 5e- and 5f-loops; a conserved tryptophan inserts into the 5e-loop forming a novel K+-turn RNA kink; SRP72-RBD remodels the 5f-loop involved in ribosome binding; cryo-EM docking reveals multiple contact sites of SRP68/72 with the ribosome. |
X-ray crystallography, cryo-EM docking, mutagenesis |
Nucleic acids research |
High |
27899666
|
| 2017 |
Crystal structures of human apo-SRP72 and the SRP68/72 complex reveal that SRP72's SRP68-binding domain contains four atypical TPR repeats and a flexible C-terminal cap; apo-SRP72 exists as a homodimer in solution; binding of SRP68 requires SRP72 homodimer dissociation and a conformational change of the C-terminal cap; a 23-residue polypeptide of SRP68 is sufficient for tight binding to SRP72 via an unusually hydrophobic extended surface; cancer-associated mutations disrupt SRP68-SRP72 interaction and their co-localization with ER. |
X-ray crystallography (2.91 Å apo-SRP72, 1.7 Å SRP68/72 complex), biophysical assays, site-directed mutagenesis, cell imaging |
Journal of molecular cell biology |
High |
28369529
|
| 2019 |
Reconstituted human SRP68/72 exhibits ultrasensitive (nanomolar) binding to human ribosomes with avidity from multiple binding sites dominated by the C-terminus of SRP72; SRP RNA alone does not bind the ribosome; intact SRP binds ribosomes with nanomolar affinity via a two-step mechanism centered on SRP54. |
Large-scale recombinant reconstitution of all human SRP components, microscale thermophoresis binding assays |
Nucleic acids research |
High |
30649417
|
| 2017 |
CELF1 directly binds SRP68 mRNA and destabilizes it; overexpression of SRP68 alone is sufficient to cause SRP subunit imbalance, impair secretion, and disrupt wound healing in myoblasts, demonstrating that stoichiometric control of SRP68 is critical for SRP function in secretion. |
RNA immunoprecipitation, in vitro binding assays, mRNA half-life measurement, overexpression with functional readouts (secretion assay, wound healing) |
PloS one |
Medium |
28129347
|
| 2024 |
Cryo-EM structure of full-length SRP68/72 reveals an extended dimerization domain that is both a protein- and RNA-binding domain; SRP68 and SRP72 depend on each other for stability; comparative structural analysis suggests the dimerization domain undergoes large-scale translocation upon SRP docking onto SRP receptor, positioning it to bind and release the Alu domain (SRP9/14) from the ribosomal surface to terminate elongation arrest. |
Cryo-EM structure of full-length SRP68/72, comparative structural analysis with existing models |
Nucleic acids research |
High |
38366771
|