scholarly journals Cancer associated mutations in Sec61γ alter the permeability of the ER translocase

PLoS Genetics ◽  
2021 ◽  
Vol 17 (8) ◽  
pp. e1009780
Author(s):  
Christopher M. Witham ◽  
Aleshanee L. Paxman ◽  
Lamprini Baklous ◽  
Robert F. L. Steuart ◽  
Benjamin L. Schulz ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Complex ◽  
Integral Membrane Proteins ◽  
Permeability Barrier ◽  
Malignant Cells ◽  
Conducting Channel ◽  
Genome Database ◽  
C Terminus ◽  
Progression Of Disease ◽  
Conserved Amino Acids

Translocation of secretory and integral membrane proteins across or into the ER membrane occurs via the Sec61 complex, a heterotrimeric protein complex possessing two essential sub-units, Sec61p/Sec61α and Sss1p/Sec61γ and the non-essential Sbh1p/Sec61β subunit. In addition to forming a protein conducting channel, the Sec61 complex maintains the ER permeability barrier, preventing flow of molecules and ions. Loss of Sec61 integrity is detrimental and implicated in the progression of disease. The Sss1p/Sec61γ C-terminus is juxtaposed to the key gating module of Sec61p/Sec61α and is important for gating the translocon. Inspection of the cancer genome database identifies six mutations in highly conserved amino acids of Sec61γ/Sss1p. We identify that five out of the six mutations identified affect gating of the ER translocon, albeit with varying strength. Together, we find that mutations in Sec61γ that arise in malignant cells result in altered translocon gating dynamics, this offers the potential for the translocon to represent a target in co-therapy for cancer treatment.

Biogenesis of tail-anchored proteins

2003 ◽  
Vol 31 (6) ◽  
pp. 1238-1242 ◽  
Author(s):  
N. Borgese ◽  
S. Brambillasca ◽  
P. Soffientini ◽  
M. Yabal ◽  
M. Makarow
Keyword(s):  
Amino Acids ◽  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Recent Work ◽  
Integral Membrane Proteins ◽  
Phospholipid Bilayer ◽  
Endoplasmic Reticulum Membrane ◽  
Regulatory Processes ◽  
C Terminus ◽  
Hydrophobic Amino Acids

A group of integral membrane proteins, known as C-tail anchored, is defined by the presence of a cytosolic N-terminal domain that is anchored to the phospholipid bilayer by a single segment of hydrophobic amino acids close to the C-terminus. The mode of insertion into membranes of these proteins, many of which play key roles in fundamental intracellular processes, is obligatorily post-translational, is highly specific and may be subject to regulatory processes that modulate the protein's function. Recent work has demonstrated that tail-anchored proteins translocate their C-termini across the endoplasmic reticulum membrane by a mechanism different from that used for Sec61-dependent post-translational signal-peptide-driven translocation. Here we summarize recent results on the insertion of tail-anchored proteins and discuss possible mechanisms that could be involved.

scholarly journals Identification of the domains in cyclin A required for binding to, and activation of, p34cdc2 and p32cdk2 protein kinase subunits.

1992 ◽  
Vol 3 (11) ◽  
pp. 1279-1294 ◽  
Author(s):  
H Kobayashi ◽  
E Stewart ◽  
R Poon ◽  
J P Adamczewski ◽  
J Gannon ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Kinase ◽  
Point Mutations ◽  
Cyclin A ◽  
Protein Kinase Activity ◽  
Large Deletions ◽  
C Terminus ◽  
M Phase ◽  
Free Translation ◽  
Conserved Amino Acids

The binding of cyclin A to p34cdc2 and p32cdk2 and the protein kinase activity of the complexes has been measured by cell-free translation of the corresponding mRNA in extracts of frog eggs, followed by immunoprecipitation. A variety of mutant cyclin A molecules have been constructed and tested in this assay. Small deletions and point mutations of highly conserved residues in the 100-residue "cyclin box" abolish binding and activation of both p34cdc2 and p32cdk2. By contrast, large deletions at the N-terminus have no effect on kinase binding and activation, until they remove residues beyond 161, where the first conserved amino acids are found in all known examples of cyclin A. At the C-terminus, removal of 14 or more amino acids abolishes activity. We also demonstrate that deletion of, or point mutations, in the cyclin A homologue of the 10-residue "destruction box," previously described in cyclin B (Glotzer et al., 1991) abolish cyclin proteolysis at the transition from M-phase to interphase.

scholarly journals The conserved C-terminus of Sss1p is required to maintain the endoplasmic reticulum permeability barrier

2019 ◽  
Vol 295 (7) ◽  
pp. 2125-2134
Author(s):  
Christopher M. Witham ◽  
Hasindu G. Dassanayake ◽  
Aleshanee L. Paxman ◽  
Kofi L. P. Stevens ◽  
Lamprini Baklous ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Pathway ◽  
Permeability Barrier ◽  
Temperature Sensitive ◽  
Er Stress Response ◽  
C Terminus ◽  
Evolutionarily Conserved ◽  
Protein Biogenesis ◽  
Progression Of Disease ◽  
Two Temperature

The endoplasmic reticulum (ER) is the entry point to the secretory pathway and major site of protein biogenesis. Translocation of secretory and integral membrane proteins across or into the ER membrane occurs via the evolutionarily conserved Sec61 complex, a heterotrimeric channel that comprises the Sec61p/Sec61α, Sss1p/Sec61γ, and Sbh1p/Sec61β subunits. In addition to forming a protein-conducting channel, the Sec61 complex also functions to maintain the ER permeability barrier, preventing the mass free flow of essential ER-enriched molecules and ions. Loss in Sec61 integrity is detrimental and implicated in the progression of disease. The Sss1p/Sec61γ C terminus is juxtaposed to the key gating module of Sec61p/Sec61α, and we hypothesize it is important for gating the ER translocon. The ER stress response was found to be constitutively induced in two temperature-sensitive sss1 mutants (sss1ts) that are still proficient to conduct ER translocation. A screen to identify intergenic mutations that allow for sss1ts cells to grow at 37 °C suggests the ER permeability barrier to be compromised in these mutants. We propose the extreme C terminus of Sss1p/Sec61γ is an essential component of the gating module of the ER translocase and is required to maintain the ER permeability barrier.

Human Platelet Antigen 3 (HPA-3): Localization of the Determinant of the Alloantibody Leka (HPA-3a) to the C-Terminus of Platelet Glycoprotein IIb Heavy Chain and Contribution of O-Linked Carbohydrates

1993 ◽  
Vol 69 (05) ◽  
pp. 485-489 ◽  
Author(s):  
Isabelle Djaffar ◽  
Didier Vilette ◽  
Dominique Pidard ◽  
Jean-Luc Wautier ◽  
Jean-Philippe Rosa
Keyword(s):  
Amino Acids ◽  
Heavy Chain ◽  
Human Platelet ◽  
Platelet Glycoprotein ◽  
Fibrinogen Receptor ◽  
C Terminus ◽  
Platelet Antigen ◽  
Human Platelet Antigen ◽  
Determinant Structure ◽  
Polymerase Chain

SummaryThe human platelet antigen (HPA) 3 system is expressed on GPIIb, one subunit of GPIIb-IIIa, the platelet fibrinogen receptor. It was recently shown that HPA-3 was associated with an Ile843/Ser polymorphism. To investigate further HPA-3 determinant structure, we localized an HPA-3a determinant, recognized by the alloantiserum Leka, within the last 29 amino acids of GPIIbα. This region encompasses the polymorphic Ile843, which, as expected, is substituted into Ser in Leka-negative individuals, as shown by DNA sequence after polymerase chain reaction on platelet RNA. In addition, contribution of glycosylation to the determinant structure was demonstrated since the Leka antigenicity was strongly decreased after specifically removing nonterminal O-linked sugars, but not terminal sialic acids. We have thus refined the localization of an HPA-3a determinant within the last 29 amino acids, including Ile843, of GPIIb heavy chain, and shown that the Leka HPA-3a determinant is dependent, in part, upon the serine-linked carbohydrates adjacent to Ile/Ser843.

scholarly journals The Amino Acids Motif -32GSSYN36- in the Catalytic Domain of E. coli Flavorubredoxin NO Reductase Is Essential for Its Activity

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 926
Author(s):  
Maria C. Martins ◽  
Susana F. Fernandes ◽  
Bruno A. Salgueiro ◽  
Jéssica C. Soares ◽  
Célia V. Romão ◽  
...  
Keyword(s):  
Amino Acids ◽  
Catalytic Domain ◽  
Reductase Activity ◽  
Conserved Residues ◽  
Mutant Proteins ◽  
E Coli ◽  
C Terminus ◽  
Bona Fide ◽  
Oxygen Reductase ◽  
Soluble Enzymes

Flavodiiron proteins (FDPs) are a family of modular and soluble enzymes endowed with nitric oxide and/or oxygen reductase activities, producing N2O or H2O, respectively. The FDP from Escherichia coli, which, apart from the two core domains, possesses a rubredoxin-like domain at the C-terminus (therefore named flavorubredoxin (FlRd)), is a bona fide NO reductase, exhibiting O2 reducing activity that is approximately ten times lower than that for NO. Among the flavorubredoxins, there is a strictly conserved amino acids motif, -G[S,T]SYN-, close to the catalytic diiron center. To assess its role in FlRd’s activity, we designed several site-directed mutants, replacing the conserved residues with hydrophobic or anionic ones. The mutants, which maintained the general characteristics of the wild type enzyme, including cofactor content and integrity of the diiron center, revealed a decrease of their oxygen reductase activity, while the NO reductase activity—specifically, its physiological function—was almost completely abolished in some of the mutants. Molecular modeling of the mutant proteins pointed to subtle changes in the predicted structures that resulted in the reduction of the hydration of the regions around the conserved residues, as well as in the elimination of hydrogen bonds, which may affect proton transfer and/or product release.

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