| 1996 |
OST4 encodes an unusually small 36-amino-acid (~3.6 kDa) protein that is required for normal oligosaccharyltransferase (OTase) activity in yeast; deletion of OST4 greatly diminishes but does not abolish OTase activity in vivo and in vitro, and the null mutant is inviable at 37°C, demonstrating OST4 is an essential OTase subunit or accessory component at high temperature. |
Genetic disruption/null mutant analysis, in vivo and in vitro OTase activity assays, biochemical characterization of the OST4 gene product |
The Journal of biological chemistry |
High |
8621712
|
| 1997 |
Ost4p (3.6 kDa) is a bona fide subunit of the yeast oligosaccharyltransferase complex present in equimolar stoichiometry with seven other subunits; mild denaturation of the immunoprecipitated complex releases a stable subcomplex comprising Stt3p, Ost3p, and Ost4p, indicating Ost4p bridges these two subunits within the OST. |
Epitope-tagging of Ost3p, co-immunoprecipitation of all OST subunits, quantification of radiolabeled subunits, partial denaturation to isolate subcomplexes |
The Journal of biological chemistry |
High |
9405463
|
| 1997 |
Overexpression of OST4 suppresses conditional stt3 alleles in yeast, providing genetic epistasis evidence that Ost4p functionally interacts with the catalytic Stt3p subunit of the OST complex. |
Genetic suppressor analysis — overexpression of OST4 in stt3 conditional mutants |
Molecular & general genetics : MGG |
Medium |
9435788
|
| 2003 |
Ost4p adopts an N(lumen)-C(cyto) type I membrane topology in the ER membrane, with its transmembrane segment spanning residues ~10–25; mutation of residues 18–25 to ionizable amino acids disrupts interactions with both Stt3p and Ost3p, and ost4 temperature-sensitive mutants cause loss of direct Ost3p–Stt3p interaction, demonstrating that the cytoplasmic-leaflet region of Ost4p physically bridges Ost3p and Stt3p in the OST subcomplex. |
In vivo membrane topology determination, site-directed mutagenesis of transmembrane residues, CD analysis of synthetic Ost4p in liposomes, co-immunoprecipitation in ost4 mutant backgrounds |
Proceedings of the National Academy of Sciences of the United States of America |
High |
12810948
|
| 2005 |
Ost4p is required for the assembly of two functionally distinct OST complexes in yeast: one containing Ost3p and one containing Ost6p. In the absence of Ost4p, neither Ost3p nor Ost6p is incorporated into the OST complex, showing that Ost4p is essential for the assembly of both OST isoforms. |
Blue native gel electrophoresis of OST complexes from wild-type and ost4 deletion strains, immunodetection of individual subunits |
Glycobiology |
High |
16096346
|
| 2005 |
The eukaryotic OST complex in yeast contains Ost4p as one of eight equimolar subunits, and the STT3 subunit is critical for catalytic activity; Ost4p participates in the Stt3p-Ost3p/Ost6p subcomplex. |
Review synthesizing co-immunoprecipitation, blue native gel, and genetic evidence from multiple laboratories |
Glycobiology |
Medium |
16317064
|
| 2011 |
Solution NMR of human OST4 in detergent solvent reveals that residues 5–30 adopt an α-helical structure with a kink in the transmembrane domain, providing the first structural characterization of the human OST4 protein. |
NMR spectroscopy (solution structure determination in detergent) |
Biochemical and biophysical research communications |
Medium |
21609714
|
| 2013 |
Human OST4 is assembled into native OST complexes containing either the catalytic STT3A or STT3B isoforms; OST4 co-immunoprecipitates with both STT3 isoforms and with ribophorin I; a single amino acid change in the OST4 transmembrane region perturbs these interactions; siRNA depletion of OST4 destabilizes native OST complexes (producing a novel ribophorin I subcomplex) and causes a defect in N-glycosylation of endogenous prosaposin similar to STT3A depletion, consistent with OST4 stabilizing STT3A-containing isoforms for co-translational N-glycosylation. |
Co-immunoprecipitation, site-directed mutagenesis of transmembrane domain, siRNA knockdown, blue native gel electrophoresis, N-glycosylation assay of endogenous substrate (prosaposin) |
Journal of cell science |
High |
23606741
|
| 2021 |
NMR solution structures and MD simulations of yeast Ost4 and the V23D mutant show that while the V23D point mutation does not alter the overall helical structure of Ost4, it changes its position and solvent exposure in the membrane-mimetic environment; MD simulations of the membrane-embedded OST complex show that V23D disrupts hydrophobic helix–helix interactions between Ost4 and TM12/TM13 of Stt3, causing disengagement of Ost4V23D and exposure of residue D23 in the hydrophobic pocket, providing a structural mechanism for OST complex destabilization. |
Solution NMR structure determination (micelles), molecular dynamics simulations of membrane-bound OST complex with WT and V23D Ost4 |
Glycobiology |
Medium |
33442744
|
| 2024 |
Solid-state NMR of yeast Ost4 and Ost4V23D reconstituted in POPC/POPE lipid bilayers shows significant chemical shift changes upon V23D mutation, indicating a dramatic change in the chemical environment of the transmembrane helix in a native-like lipid bilayer context. |
Solid-state NMR with magic-angle spinning, reconstitution in lipid bilayers |
Journal of biomolecular NMR |
Medium |
38421550
|
| 2025 |
Ost4 is a substrate of the AAA+ ATPase Msp1 when mislocalized to mitochondria; an Msp1-protease chimera captures Ost4 as a novel Msp1 substrate by mass spectrometry; topology experiments show that mislocalized Ost4 adopts mixed membrane orientations at mitochondria, and Msp1 extracts mislocalized Ost4 regardless of its orientation. |
Msp1-protease chimera (substrate trapping), mass spectrometry identification, topology assay of mislocalized Ost4 |
bioRxivpreprint |
Medium |
40236206
|