scholarly journals The role of membrane phospholipids in the interaction of ribosomes with endoplasmic-reticulum membrane (Short Communication)

1973 ◽  
Vol 132 (3) ◽  
pp. 637-640 ◽  
Author(s):  
S. Jothy ◽  
S. Tay ◽  
H. Simpkins
Keyword(s):  
Endoplasmic Reticulum ◽  
Short Communication ◽  
Endoplasmic Reticulum Membrane ◽  
Membrane Phospholipids ◽  
Binding Process ◽  
Head Groups ◽  
Membrane Components

It is shown that the ionic head groups of the membrane phospholipids cannot be solely responsible for the attachment of the ribosome and that other membrane components must also be involved in the binding process.

scholarly journals Structural and functional characterization of Sec66p, a new subunit of the polypeptide translocation apparatus in the yeast endoplasmic reticulum.

1993 ◽  
Vol 4 (9) ◽  
pp. 931-939 ◽  
Author(s):  
D Feldheim ◽  
K Yoshimura ◽  
A Admon ◽  
R Schekman
Keyword(s):  
Endoplasmic Reticulum ◽  
Signal Sequence ◽  
Functional Characterization ◽  
Yeast Cells ◽  
Temperature Sensitive ◽  
Endoplasmic Reticulum Membrane ◽  
Restrictive Temperature ◽  
Permissive Temperature

SEC66 encodes the 31.5-kDa glycoprotein of the Sec63p complex, an integral endoplasmic reticulum membrane protein complex required for translocation of presecretory proteins in Saccharomyces cerevisiae. DNA sequence analysis of SEC66 predicts a 23-kDa protein with no obvious NH2-terminal signal sequence but with one domain of sufficient length and hydrophobicity to span a lipid bilayer. Antibodies directed against a recombinant form of Sec66p were used to confirm the membrane location of Sec66p and that Sec66p is a glycoprotein of 31.5 kDa. A null mutation in SEC66 renders yeast cells temperature sensitive for growth. sec66 cells accumulate some secretory precursors at a permissive temperature and a variety of precursors at the restrictive temperature. sec66 cells show defects in Sec63p complex formation. Because sec66 cells affect the translocation of some, but not all secretory precursor polypeptides, the role of Sec66p may be to interact with the signal peptide of presecretory proteins.

scholarly journals Sls1p Stimulates Sec63p-Mediated Activation of Kar2p in a Conformation-Dependent Manner in the Yeast Endoplasmic Reticulum

2000 ◽  
Vol 20 (18) ◽  
pp. 6923-6934 ◽  
Author(s):  
Mehdi Kabani ◽  
Jean-Marie Beckerich ◽  
Claude Gaillardin
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Translocation ◽  
Synthetic Lethality ◽  
In Vitro Assays ◽  
Endoplasmic Reticulum Membrane ◽  
Dependent Manner ◽  
Dose Dependent

ABSTRACT We previously characterized the SLS1 gene in the yeastYarrowia lipolytica and showed that it interacts physically with YlKar2p to promote translocation across the endoplasmic-reticulum membrane (A. Boisramé, M. Kabani, J. M. Beckerich, E. Hartmann, and C. Gaillardin, J. Biol. Chem. 273:30903–30908, 1998). A Y. lipolytica Kar2p mutant was isolated that restored interaction with an Sls1p mutant, suggesting that the interaction with Sls1p could be nucleotide and/or conformation dependent. This result was used as a working hypothesis for more accurate investigations in Saccharomyces cerevisiae. We show by two-hybrid an in vitro assays that the S. cerevisiae homologue of Sls1p interacts with ScKar2p. Using dominant lethal mutants of ScKar2p, we were able to show that ScSls1p preferentially interacts with the ADP-bound conformation of the molecular chaperone. Synthetic lethality was observed between ΔScsls1 and translocation-deficientkar2 or sec63-1 mutants, providing in vivo evidence for a role of ScSls1p in protein translocation. Synthetic lethality was also observed with ER-associated degradation and folding-deficient kar2 mutants, strongly suggesting that Sls1p functions are not restricted to the translocation process. We show that Sls1p stimulates in a dose-dependent manner the binding ofScKar2p on the lumenal J domain of Sec63p fused to glutathione S-transferase. Moreover, Sls1p is shown to promote the Sec63p-mediated activation of Kar2p's ATPase activity. Our data strongly suggest that Sls1p could be the first GrpE-like protein described in the endoplasmic reticulum.

scholarly journals Divalent Cation Modulation of Ion Permeation in TMEM16 Proteins

2021 ◽  
Vol 22 (4) ◽  
pp. 2209
Author(s):  
Dung M. Nguyen ◽  
Hwoi Chan Kwon ◽  
Tsung-Yu Chen
Keyword(s):  
Alkaline Earth ◽  
Divalent Cations ◽  
Transmembrane Protein ◽  
Ion Selectivity ◽  
Physiological Role ◽  
Ion Permeation ◽  
Membrane Phospholipids ◽  
Anion Channels ◽  
Head Groups

Intracellular divalent cations control the molecular function of transmembrane protein 16 (TMEM16) family members. Both anion channels (such as TMEM16A) and phospholipid scramblases (such as TMEM16F) in this family are activated by intracellular Ca2+ in the low µM range. In addition, intracellular Ca2+ or Co2+ at mM concentrations have been shown to further potentiate the saturated Ca2+-activated current of TMEM16A. In this study, we found that all alkaline earth divalent cations in mM concentrations can generate similar potentiation effects in TMEM16A when applied intracellularly, and that manipulations thought to deplete membrane phospholipids weaken the effect. In comparison, mM concentrations of divalent cations minimally potentiate the current of TMEM16F but significantly change its cation/anion selectivity. We suggest that divalent cations may increase local concentrations of permeant ions via a change in pore electrostatic potential, possibly acting through phospholipid head groups in or near the pore. Monovalent cations appear to exert a similar effect, although with a much lower affinity. Our findings resolve controversies regarding the ion selectivity of TMEM16 proteins. The physiological role of this mechanism, however, remains elusive because of the nearly constant high cation concentrations in cytosols.

scholarly journals Role of OAT2 as Endoplasmic Reticulum Membrane Transporters in Bumetanide Glucuronidation

2019 ◽  
Vol 33 (S1) ◽  
Author(s):  
Hiroshi Arakawa ◽  
Karin Araya ◽  
Yusuke Masuo ◽  
Tomohiko Wakayama ◽  
Yukio Kato
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Transporters ◽  
Endoplasmic Reticulum Membrane

scholarly journals PACS-2 attenuates diabetic kidney disease via the enhancement of mitochondria-associated endoplasmic reticulum membrane formation

2021 ◽  
Vol 12 (12) ◽  
Author(s):  
Mei Xue ◽  
Ting Fang ◽  
Hongxi Sun ◽  
Ying Cheng ◽  
Ting Li ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Kidney Disease ◽  
Diabetic Kidney Disease ◽  
Pathological Process ◽  
Endoplasmic Reticulum Membrane ◽  
Protective Effects ◽  
Diabetic Kidney ◽  
Renal Tubular

AbstractThe altered homeostasis of mitochondria-associated endoplasmic reticulum (ER) membranes (MAM) was closely associated with the pathological process of nervous system diseases and insulin resistance. Here, the exact implication of phosphofurin acidic cluster sorting protein 2 (PCAS-2), an anchor protein in the MAM interface, in diabetic kidney disease was investigated. In the kidneys of type 1 and type 2 diabetes mice and HG-induced HK-2 cells, a notable disruption of ER-mitochondria interactions, accompanied by a decreased PACS-2 expression in all subcellular fractions. Furthermore, PACS-2 knockout mice with diabetes displayed accelerated development of proteinuria, deterioration of kidney function, and aggravated disruption of MAM area, ER stress, mitochondrial dysfunction, renal apoptosis, and fibrosis. However, overexpression of PACS-2 effectively protected diabetic kidneys and HG-treated HK-2 cells from renal tubular impairments. Importantly, experimental uncoupling of ER-mitochondria contacts reversed the protective effects of PACS-2 restoration on HK-2 cells under HG conditions. In summary, our data indicate a pivotal role of PACS-2 in the development of diabetic renal tubular injury via the stabilization of MAM.

scholarly journals The cellular origin of glyoxysomal proteins in germinating castor-bean endosperm

1976 ◽  
Vol 154 (2) ◽  
pp. 501-506 ◽  
Author(s):  
L Bowden ◽  
J. M Lord
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Synthesis ◽  
Castor Bean ◽  
Developmental Stages ◽  
Endoplasmic Reticulum Membrane ◽  
Endosperm Tissue ◽  
Cellular Origin ◽  
Lag Period ◽  
Kinetics Of

The capacity of castor-bean endosperm tissue to incorporate [35S]methionine into proteins of the total particulate fraction increased during the first 3 days of germination and subsequently declined. At the onset of germination 66% of the incorporated 35S was found in the separated endoplasmic-reticulum fraction, with the remainder in mitochondria, whereas at later developmental stages an increasing proportion of 35S was recovered in glyoxysomes. The kinetics of [35S]methionine incorporation into the major organelle fractions of 3-day-old endosperm tissue showed that the endoplasmic reticulum was immediately labelled, whereas a lag period preceded the labelling of mitochondria and glyoxysomes. When kinetic experiments were interrupted by the addition of an excess of unlabelled methionine, incorporation of [35S]methionine into the endoplasmic reticulum rapidly ceased, but incorporation into mitochondia and glyoxysomes continued for a further 1h. Examination of isolated organelle membranes during this period showed that the addition of unlabelled methionine resulted in a stimulated incorporation of [35S]no methionine into the endoplasmic-reticulum membrane for 30 min, after which time the 35S content of this fraction declined, whereas that of the glyoxysomal membranes continued to increase slowly. The 35S-labelling kinetics of organelles and fractions derived therefrom are discussed in relation to the role of the endoplasmic reticulum in protein synthesis during glyoxysome biogenesis.

scholarly journals Sec61p Serves Multiple Roles in Secretory Precursor Binding and Translocation into the Endoplasmic Reticulum Membrane

1998 ◽  
Vol 9 (12) ◽  
pp. 3455-3473 ◽  
Author(s):  
Marinus Pilon ◽  
Karin Römisch ◽  
Dong Quach ◽  
Randy Schekman
Keyword(s):  
Endoplasmic Reticulum ◽  
Receptor Site ◽  
Multiple Roles ◽  
Secretory Proteins ◽  
Endoplasmic Reticulum Membrane ◽  
Wild Type ◽  
Evolutionarily Conserved ◽  
Cold Sensitive ◽  
A Subunit

The evolutionarily conserved Sec61 protein complex mediates the translocation of secretory proteins into the endoplasmic reticulum. To investigate the role of Sec61p, which is the main subunit of this complex, we generated recessive, cold-sensitive alleles ofsec61 that encode stably expressed proteins with strong defects in translocation. The stage at which posttranslational translocation was blocked was probed by chemical crosslinking of radiolabeled secretory precursors added to membranes isolated from wild-type and mutant strains. Two classes of sec61mutants were distinguished. The first class of mutants was defective in preprotein docking onto a receptor site of the translocon that included Sec61p itself. The second class of mutants allowed docking of precursors onto the translocon but was defective in the ATP-dependent release of precursors from this site that in wild-type membranes leads to pore insertion and full translocation. Only mutants of the second class were partially suppressed by overexpression ofSEC63, which encodes a subunit of the Sec61 holoenzyme complex responsible for positioning Kar2p (yeast BiP) at the translocation channel. These mutants thus define two early stages of translocation that require SEC61 function before precursor protein transfer across the endoplasmic reticulum membrane.

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