scholarly journals Differential expression and function of two homologous subunits of yeast 1,3-beta-D-glucan synthase.

1995 ◽  
Vol 15 (10) ◽  
pp. 5671-5681 ◽  
Author(s):  
P Mazur ◽  
N Morin ◽  
W Baginsky ◽  
M el-Sherbeini ◽  
J A Clemas ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Function Analysis ◽  
Calcineurin Inhibitors ◽  
Integral Membrane Protein ◽  
Dependent Manner ◽  
Fungal Cell ◽  
Glucan Synthase ◽  
Increased Sensitivity ◽  
And Function ◽  
Null Mutants

1,3-beta-D-Glucan is a major structural polymer of yeast and fungal cell walls and is synthesized from UDP-glucose by the multisubunit enzyme 1,3-beta-D-glucan synthase. Previous work has shown that the FKS1 gene encodes a 215-kDa integral membrane protein (Fks1p) which mediates sensitivity to the echinocandin class of antifungal glucan synthase inhibitors and is a subunit of this enzyme. We have cloned and sequenced FKS2, a homolog of FKS1 encoding a 217-kDa integral membrane protein (Fks2p) which is 88% identical to Fks1p. The residual glucan synthase activity present in strains with deletions of fks1 is (i) immunodepleted by antibodies prepared against FKS2 peptides, demonstrating that Fks2p is also a component of the enzyme, and (ii) more sensitive to the echinocandin L-733,560, explaining the increased sensitivity of fks1 null mutants to this drug. Simultaneous disruption of FKS1 and FKS2 is lethal, suggesting that Fks1p and Fks2p are alternative subunits with essential overlapping function. Analysis of FKS1 and FKS2 expression reveals that transcription of FKS1 is regulated in the cell cycle and predominates during growth on glucose, while FKS2 is expressed in the absence of glucose. FKS2 is essential for sporulation, a process which occurs during nutritional starvation. FKS2 is induced by the addition of Ca2+ to the growth medium, and this induction is completely dependent on the Ca2+/calmodulin-dependent phosphoprotein phosphatase calcineurin. We have previously shown that growth of fks1 null mutants is highly sensitive to the calcineurin inhibitors FK506 and cyclosporin A. Expression of FKS2 from the heterologous ADH1 promoter results in FK506-resistant growth. Thus, the sensitivity of fks1 mutants to these drugs can be explained by the calcineurin-dependent transcription of FKS2. Moreover, FKS2 is also highly induced in response to pheromone in a calcineurin-dependent manner, suggesting that FKS2 may also play a role in the remodeling of the cell wall during the mating process.

scholarly journals The Saccharomyces cerevisiae FKS1 (ETG1) gene encodes an integral membrane protein which is a subunit of 1,3-beta-D-glucan synthase.

1994 ◽  
Vol 91 (26) ◽  
pp. 12907-12911 ◽  
Author(s):  
C. M. Douglas ◽  
F. Foor ◽  
J. A. Marrinan ◽  
N. Morin ◽  
J. B. Nielsen ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Protein ◽  
Integral Membrane Protein ◽  
Glucan Synthase ◽  
A Subunit

scholarly journals Characterization of YmgF, a 72-Residue Inner Membrane Protein That Associates with the Escherichia coli Cell Division Machinery

2008 ◽  
Vol 191 (1) ◽  
pp. 333-346 ◽  
Author(s):  
Gouzel Karimova ◽  
Carine Robichon ◽  
Daniel Ladant
Keyword(s):  
Escherichia Coli ◽  
Cell Division ◽  
Membrane Protein ◽  
Integral Membrane Protein ◽  
Dependent Manner ◽  
E Coli ◽  
Division Site ◽  
Inner Membrane Protein ◽  
Two Hybrid

ABSTRACT Formation of the Escherichia coli division septum is catalyzed by a number of essential proteins (named Fts) that assemble into a ring-like structure at the future division site. Many of these Fts proteins are intrinsic transmembrane proteins whose functions are largely unknown. In the present study, we attempted to identify a novel putative component(s) of the E. coli cell division machinery by searching for proteins that could interact with known Fts proteins. To do that, we used a bacterial two-hybrid system based on interaction-mediated reconstitution of a cyclic AMP (cAMP) signaling cascade to perform a library screening in order to find putative partners of E. coli cell division protein FtsL. Here we report the characterization of YmgF, a 72-residue integral membrane protein of unknown function that was found to associate with many E. coli cell division proteins and to localize to the E. coli division septum in an FtsZ-, FtsA-, FtsQ-, and FtsN-dependent manner. Although YmgF was previously shown to be not essential for cell viability, we found that when overexpressed, YmgF was able to overcome the thermosensitive phenotype of the ftsQ1(Ts) mutation and restore its viability under low-osmolarity conditions. Our results suggest that YmgF might be a novel component of the E. coli cell division machinery.

scholarly journals A previously unrecognized membrane protein in the Rhodobacter sphaeroides LH1-RC photocomplex

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kazutoshi Tani ◽  
Kenji V. P. Nagashima ◽  
Ryo Kanno ◽  
Saki Kawamura ◽  
Riku Kikuchi ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Ring Opening ◽  
Model Organism ◽  
Hypothetical Protein ◽  
Integral Membrane Protein ◽  
Bacterial Photosynthesis ◽  
Core Complex ◽  
Rc Structures ◽  
Complex Forms ◽  
And Function

AbstractRhodobacter (Rba.) sphaeroides is the most widely used model organism in bacterial photosynthesis. The light-harvesting-reaction center (LH1-RC) core complex of this purple phototroph is characterized by the co-existence of monomeric and dimeric forms, the presence of the protein PufX, and approximately two carotenoids per LH1 αβ-polypeptides. Despite many efforts, structures of the Rba. sphaeroides LH1-RC have not been obtained at high resolutions. Here we report a cryo-EM structure of the monomeric LH1-RC from Rba. sphaeroides strain IL106 at 2.9 Å resolution. The LH1 complex forms a C-shaped structure composed of 14 αβ-polypeptides around the RC with a large ring opening. From the cryo-EM density map, a previously unrecognized integral membrane protein, referred to as protein-U, was identified. Protein-U has a U-shaped conformation near the LH1-ring opening and was annotated as a hypothetical protein in the Rba. sphaeroides genome. Deletion of protein-U resulted in a mutant strain that expressed a much-reduced amount of the dimeric LH1-RC, indicating an important role for protein-U in dimerization of the LH1-RC complex. PufX was located opposite protein-U on the LH1-ring opening, and both its position and conformation differed from that of previous reports of dimeric LH1-RC structures obtained at low-resolution. Twenty-six molecules of the carotenoid spheroidene arranged in two distinct configurations were resolved in the Rba. sphaeroides LH1 and were positioned within the complex to block its channels. Our findings offer an exciting new view of the core photocomplex of Rba. sphaeroides and the connections between structure and function in bacterial photocomplexes in general.

scholarly journals A Novel Membrane Protein in the Rhodobacter sphaeroides LH1-RC Photocomplex

2021 ◽  
Author(s):  
K. Tani ◽  
K. V. P. Nagashima ◽  
R. Kanno ◽  
S. Kawamura ◽  
R. Kikuchi ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Ring Opening ◽  
Hypothetical Protein ◽  
Integral Membrane Protein ◽  
Purple Bacterium ◽  
Core Complex ◽  
Rc Structures ◽  
Density Map ◽  
Complex Forms ◽  
And Function

We present a cryo-EM structure of the monomeric light-harvesting-reaction center (LH1-RC) core complex from photosynthetic purple bacterium Rhodobacter (Rba.) sphaeroides at 2.9 Å resolution. The LH1 complex forms a C-shaped structure composed of 14 αβ-polypeptides around the RC with a large ring opening. From the cryo-EM density map, a previously unrecognized integral membrane protein, referred to as protein-U, was identified. Protein-U has a U-shaped conformation near the LH1-ring opening and was annotated as a hypothetical protein in the Rba. sphaeroides genome. Deletion of protein-U resulted in a mutant strain that expressed a much-reduced amount of the dimeric LH1-RC, indicating an important role for protein-U in dimerization of the LH1-RC complex. PufX was located opposite protein-U on the LH1-ring opening, and both its position and conformation differed from that of previous reports of dimeric LH1-RC structures obtained at low-resolution. Twenty-six molecules of the carotenoid spheroidene arranged in two distinct configurations were resolved in the Rba. sphaeroides LH1 and were positioned within the complex to block its pores. Our findings offer a new view of the core photocomplex of Rba. sphaeroides and the connections between structure and function in bacterial photocomplexes in general.

scholarly journals Epithelial membrane glycoprotein PAS-IV is related to platelet glycoprotein IIIb binding to thrombospondin but not to malaria-infected erythrocytes

Blood ◽  
1991 ◽  
Vol 77 (12) ◽  
pp. 2649-2654 ◽  
Author(s):  
B Catimel ◽  
JL McGregor ◽  
T Hasler ◽  
DE Greenwalt ◽  
RJ Howard ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Mammary Epithelial Cells ◽  
Integral Membrane Protein ◽  
Mammary Epithelial ◽  
Platelet Glycoprotein ◽  
Enzyme Linked Immunosorbent Assay ◽  
Dependent Manner ◽  
Protein Receptors ◽  
Capillary Endothelial Cells ◽  
Peptide Map

Abstract Glycoprotein (GP) IIIb (also termed GPIV or CD36) is an integral platelet membrane protein, and has been identified as a binding site for thrombospondin, collagen, and malaria-infected erythrocytes. PAS-IV is an integral membrane protein found in lactating mammary epithelial cells and capillary endothelial cells. The N-terminal sequence of PAS- IV is nearly identical to that of GPIIIb and monospecific anti-PAS-IV antibody reacts with GPIIIb, indicating that PAS-IV is structurally related to GPIIIb. In this study, human platelet GPIIIb and bovine epithelial PAS-IV were compared in terms of structural, immunologic, and functional characteristics. The two-dimensional tryptic peptide map of both intact and deglycosylated PAS-IV was highly similar but not identical to that of GPIIIb. PAS-IV and GPIIIb reacted to an equal extent with monoclonal antibodies OKM5 and OKM8 by enzyme-linked immunosorbent assay. GPIIIb bound to surface immobilized thrombospondin (TSP) in a concentration-dependent and saturable manner, with approximately 60% reduction in binding in the presence of EDTA. PAS-IV bound to TSP with similar characteristics except that maximum binding was consistently approximately 50% of that of GPIIIb and binding was not inhibited by EDTA. GPIIIb supported adhesion of Plasmodium falciparum-infected erythrocytes (PRBC) in a dose-dependent manner while no significant adhesion of PRBC to PAS-IV was observed. Our data demonstrate that while epithelial PAS-IV and platelet GPIIIb are structurally and immunologically related, there are significant differences in their functional properties. Whether this result is due to different posttranslational glycosylation modifications or that PAS- IV and GPIIIb represent a family of related cell adhesive protein receptors remains to be determined.

scholarly journals The yeast integral membrane protein Apq12 potentially links membrane dynamics to assembly of nuclear pore complexes

2007 ◽  
Vol 178 (5) ◽  
pp. 799-812 ◽  
Author(s):  
John J. Scarcelli ◽  
Christine A. Hodge ◽  
Charles N. Cole
Keyword(s):  
Membrane Protein ◽  
Integral Membrane Protein ◽  
Membrane Dynamics ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Cold Sensitive ◽  
Low Levels ◽  
Lower Temperature ◽  
Pore Complexes ◽  
And Function

Although the structure and function of components of the nuclear pore complex (NPC) have been the focus of many studies, relatively little is known about NPC biogenesis. In this study, we report that Apq12 is required for efficient NPC biogenesis in Saccharomyces cerevisiae. Apq12 is an integral membrane protein of the nuclear envelope (NE) and endoplasmic reticulum. Cells lacking Apq12 are cold sensitive for growth, and a subset of their nucleoporins (Nups), those that are primarily components of the cytoplasmic fibrils of the NPC, mislocalize to the cytoplasm. APQ12 deletion also causes defects in NE morphology. In the absence of Apq12, most NPCs appear to be associated with the inner but not the outer nuclear membrane. Low levels of benzyl alcohol, which increases membrane fluidity, prevented Nup mislocalization and restored the proper localization of Nups that had accumulated in cytoplasmic foci upon a shift to lower temperature. Thus, Apq12p connects nuclear pore biogenesis to the dynamics of the NE.

Topology and function of the integral membrane protein conferring immunity to colicin A

1989 ◽  
Vol 3 (5) ◽  
pp. 679-687 ◽  
Author(s):  
V. Geli ◽  
D. Baty ◽  
F. Pattus ◽  
C. Lazdunski
Keyword(s):  
Membrane Protein ◽  
Integral Membrane Protein ◽  
And Function

scholarly journals Epithelial membrane glycoprotein PAS-IV is related to platelet glycoprotein IIIb binding to thrombospondin but not to malaria-infected erythrocytes

Blood ◽  
1991 ◽  
Vol 77 (12) ◽  
pp. 2649-2654
Author(s):  
B Catimel ◽  
JL McGregor ◽  
T Hasler ◽  
DE Greenwalt ◽  
RJ Howard ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Mammary Epithelial Cells ◽  
Integral Membrane Protein ◽  
Mammary Epithelial ◽  
Platelet Glycoprotein ◽  
Enzyme Linked Immunosorbent Assay ◽  
Dependent Manner ◽  
Protein Receptors ◽  
Capillary Endothelial Cells ◽  
Peptide Map

Glycoprotein (GP) IIIb (also termed GPIV or CD36) is an integral platelet membrane protein, and has been identified as a binding site for thrombospondin, collagen, and malaria-infected erythrocytes. PAS-IV is an integral membrane protein found in lactating mammary epithelial cells and capillary endothelial cells. The N-terminal sequence of PAS- IV is nearly identical to that of GPIIIb and monospecific anti-PAS-IV antibody reacts with GPIIIb, indicating that PAS-IV is structurally related to GPIIIb. In this study, human platelet GPIIIb and bovine epithelial PAS-IV were compared in terms of structural, immunologic, and functional characteristics. The two-dimensional tryptic peptide map of both intact and deglycosylated PAS-IV was highly similar but not identical to that of GPIIIb. PAS-IV and GPIIIb reacted to an equal extent with monoclonal antibodies OKM5 and OKM8 by enzyme-linked immunosorbent assay. GPIIIb bound to surface immobilized thrombospondin (TSP) in a concentration-dependent and saturable manner, with approximately 60% reduction in binding in the presence of EDTA. PAS-IV bound to TSP with similar characteristics except that maximum binding was consistently approximately 50% of that of GPIIIb and binding was not inhibited by EDTA. GPIIIb supported adhesion of Plasmodium falciparum-infected erythrocytes (PRBC) in a dose-dependent manner while no significant adhesion of PRBC to PAS-IV was observed. Our data demonstrate that while epithelial PAS-IV and platelet GPIIIb are structurally and immunologically related, there are significant differences in their functional properties. Whether this result is due to different posttranslational glycosylation modifications or that PAS- IV and GPIIIb represent a family of related cell adhesive protein receptors remains to be determined.

scholarly journals Vesicle-Associated Membrane Protein 4 and Syntaxin 6 Interactions at the Chlamydial Inclusion

2013 ◽  
Vol 81 (9) ◽  
pp. 3326-3337 ◽  
Author(s):  
Emily J. Kabeiseman ◽  
Kyle Cichos ◽  
Ted Hackstadt ◽  
Andrea Lucas ◽  
Elizabeth R. Moore
Keyword(s):  
Membrane Protein ◽  
De Novo ◽  
Snare Proteins ◽  
Dependent Manner ◽  
Binding Partner ◽  
And Function ◽  
Sirna Knockdown ◽  
Interfering Rna ◽  
Chlamydial Inclusion

ABSTRACTThe predominant players in membrane fusion events are thesolubleN-ethylmaleimide-sensitive factorattachment proteinreceptor (SNARE) family of proteins. We hypothesize that SNARE proteins mediate fusion events at the chlamydial inclusion and are important for chlamydial lipid acquisition. We have previously demonstrated thattrans-Golgi SNARE syntaxin 6 localizes to the chlamydial inclusion. To investigate the role of syntaxin 6 at the chlamydial inclusion, we examined the localization and function of anothertrans-Golgi SNARE and syntaxin 6-binding partner, vesicle-associated membrane protein 4 (VAMP4), at the chlamydial inclusion. In this study, we demonstrate that syntaxin 6 and VAMP4 colocalize to the chlamydial inclusion and interact at the chlamydial inclusion. Furthermore, in the absence of VAMP4, syntaxin 6 is not retained at the chlamydial inclusion. Small interfering RNA (siRNA) knockdown of VAMP4 inhibited chlamydial sphingomyelin acquisition, correlating with a log decrease in infectious progeny. VAMP4 retention at the inclusion was shown to be dependent onde novochlamydial protein synthesis, but unlike syntaxin 6, VAMP4 recruitment is observed in a species-dependent manner. Notably, VAMP4 knockdown inhibits sphingomyelin trafficking only to inclusions in which it localizes. These data support the hypothesis that VAMP proteins play a central role in mediating eukaryotic vesicular interactions at the chlamydial inclusion and, thus, support chlamydial lipid acquisition and chlamydial development.

scholarly journals Co-operation between different targeting pathways during integration of a membrane protein

2012 ◽  
Vol 199 (2) ◽  
pp. 303-315 ◽  
Author(s):  
Rebecca Keller ◽  
Jeanine de Keyzer ◽  
Arnold J.M. Driessen ◽  
Tracy Palmer
Keyword(s):  
Membrane Protein ◽  
Protein Transport ◽  
Transmembrane Domain ◽  
Energy Coupling ◽  
Integral Membrane Protein ◽  
Transmembrane Domains ◽  
Dependent Manner ◽  
Rieske Protein ◽  
Transport Pathway ◽  
Iron Sulfur

Membrane protein assembly is a fundamental process in all cells. The membrane-bound Rieske iron-sulfur protein is an essential component of the cytochrome bc1 and cytochrome b6f complexes, and it is exported across the energy-coupling membranes of bacteria and plants in a folded conformation by the twin arginine protein transport pathway (Tat) transport pathway. Although the Rieske protein in most organisms is a monotopic membrane protein, in actinobacteria, it is a polytopic protein with three transmembrane domains. In this work, we show that the Rieske protein of Streptomyces coelicolor requires both the Sec and the Tat pathways for its assembly. Genetic and biochemical approaches revealed that the initial two transmembrane domains were integrated into the membrane in a Sec-dependent manner, whereas integration of the third transmembrane domain, and thus the correct orientation of the iron-sulfur domain, required the activity of the Tat translocase. This work reveals an unprecedented co-operation between the mechanistically distinct Sec and Tat systems in the assembly of a single integral membrane protein.

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