scholarly journals The Role of the Cooh Terminus of Sec2p in the Transport of Post-Golgi Vesicles

2000 ◽  
Vol 149 (1) ◽  
pp. 95-110 ◽  
Author(s):  
N. Barry Elkind ◽  
Christiane Walch-Solimena ◽  
Peter J. Novick
Keyword(s):  
Full Length ◽  
Membrane Association ◽  
Secretory Vesicles ◽  
Rab Protein ◽  
Membrane Attachment ◽  
Polarized Transport ◽  
Acid Domain ◽  
Amino Acid Domain ◽  
Exchange Activity

Sec2p is required for the polarized transport of secretory vesicles in S. cerevisiae. The Sec2p NH2 terminus encodes an exchange factor for the Rab protein Sec4p. Sec2p associates with vesicles and in Sec2p COOH-terminal mutants Sec4p and vesicles no longer accumulate at bud tips. Thus, the Sec2p COOH terminus functions in targeting vesicles, however, the mechanism of function is unknown. We found comparable exchange activity for truncated and full-length Sec2 proteins, implying that the COOH terminus does not alter the exchange rate. Full-length Sec2-GFP, similar to Sec4p, concentrates at bud tips. A COOH-terminal 58–amino acid domain is necessary but not sufficient for localization. Sec2p localization depends on actin, Myo2p and Sec1p, Sec6p, and Sec9p function. Full-length, but not COOH-terminally truncated Sec2 proteins are enriched on membranes. Membrane association of full-length Sec2p is reduced in sec6-4 and sec9-4 backgrounds at 37°C but unaffected at 25°C. Taken together, these data correlate loss of localization of Sec2 proteins with reduced membrane association. In addition, Sec2p membrane attachment is substantially Sec4p independent, supporting the notion that Sec2p interacts with membranes via an unidentified Sec2p receptor, which would increase the accessibility of Sec2p exchange activity for Sec4p.

scholarly journals Role of the FtsA C Terminus as a Switch for Polymerization and Membrane Association

mBio ◽  
2014 ◽  
Vol 5 (6) ◽  
Author(s):  
Marcin Krupka ◽  
Elisa J. Cabré ◽  
Mercedes Jiménez ◽  
Germán Rivas ◽  
Ana Isabel Rico ◽  
...  
Keyword(s):  
Membrane Vesicles ◽  
Lipid Monolayers ◽  
Membrane Association ◽  
Amphipathic Helix ◽  
Content Type ◽  
Ftsz Ring ◽  
C Terminus ◽  
Membrane Attachment ◽  
Attachment Devices

ABSTRACT Together with ATP, the C-terminal region of the essential streptococcal FtsA protein acts as an intramolecular switch to promote its polymerization and attachment to the membrane. During septation, FtsA is known to anchor the constricting FtsZ ring and, subsequently, the divisome to the membrane. Truncation of the C terminus of the streptococcal FtsA (FtsAΔCt) facilitates a more rapid ATP-dependent polymerization in solution than is seen with the full-length protein (FtsA+). The FtsAΔCt polymers are more organized and compact than those formed in solution by FtsA+, resembling the shape of the membrane-associated FtsA+ polymers. We find that ATP, besides being needed for polymerization, is required for the attachment of FtsA+ to lipid monolayers and to vesicle membranes. We propose a model in which the binding of ATP activates a switch favoring the polymerization of FtsA and at the same time driving the amphipathic helix at its C terminus to become attached to the membrane. Conversely, when FtsA is in the cytoplasm, the C terminus is not engaged in the attachment to the membrane, and it obstructs polymerization. ATP-dependent polymerization of FtsA inside membrane vesicles causes vesicle shrinkage, suggesting that, besides providing a membrane attachment for FtsZ, the FtsA C terminus may also introduce local alterations in the membrane to facilitate septation. IMPORTANCE FtsA is a protein needed in many bacteria to construct a septum that divides one fully grown cell, producing two daughters. We show that the region located at the C-terminal end of the Streptococcus pneumoniae FtsA protein works as a switch triggered by ATP, a molecule that stores energy. This region contains an amphipathic helix that obstructs the assembly of FtsA into polymers in the cytoplasm. In the presence of ATP, the obstruction is removed by switching the position of the helix. The switch directs the helix to the membrane and simultaneously facilitates the polymerization of the protein. The accumulation of FtsA molecules at the membrane causes distortions, an effect produced also by proteins such as MinD, MreB, and SepF that also contain amphipathic helixes as membrane attachment devices. In the case of FtsA, these distortions may also facilitate the initial events that lead to the division of bacteria.

scholarly journals Ypt32 recruits the Sec4p guanine nucleotide exchange factor, Sec2p, to secretory vesicles; evidence for a Rab cascade in yeast

2002 ◽  
Vol 157 (6) ◽  
pp. 1005-1016 ◽  
Author(s):  
Darinel Ortiz ◽  
Martina Medkova ◽  
Christiane Walch-Solimena ◽  
Peter Novick
Keyword(s):  
Plasma Membrane ◽  
Guanine Nucleotide Exchange Factor ◽  
Secretory Vesicles ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Polarized Transport ◽  
Exchange Activity

SEC2 is an essential gene required for polarized growth of the yeast Saccharomyces cerevisiae. It encodes a protein of 759 amino acids that functions as a guanine nucleotide exchange factor for the small GTPase Sec4p, a regulator of Golgi to plasma membrane transport. Activation of Sec4p by Sec2p is needed for polarized transport of vesicles to exocytic sites. Temperature-sensitive (ts) mutations in sec2 and sec4 result in a tight block in secretion and the accumulation of secretory vesicles randomly distributed in the cell. The proper localization of Sec2p to secretory vesicles is essential for its function and is largely independent of Sec4p. Although the ts mutation sec2-78 does not affect nucleotide exchange activity, the protein is mislocalized. Here we present evidence that Ypt31/32p, members of Rab family of GTPases, regulate Sec2p function. First, YPT31/YPT32 suppress the sec2-78 mutation. Second, overexpression of Ypt31/32p restores localization of Sec2-78p. Third, Ypt32p and Sec2p interact biochemically, but Sec2p has no exchange activity on Ypt32p. We propose that Ypt32p and Sec4p act as part of a signaling cascade in which Ypt32p recruits Sec2p to secretory vesicles; once on the vesicle, Sec2p activates Sec4p, enabling the polarized transport of vesicles to the plasma membrane.

scholarly journals Structure of the full-length human Pannexin1 channel and insights into its role in pyroptosis

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Sensen Zhang ◽  
Baolei Yuan ◽  
Jordy Homing Lam ◽  
Jun Zhou ◽  
Xuan Zhou ◽  
...  
Keyword(s):  
Md Simulation ◽  
Potential Role ◽  
Md Simulations ◽  
Full Length ◽  
Inflammasome Activation ◽  
Simulation Studies ◽  
Cryo Electron Microscopy ◽  
Gating Mechanism ◽  
Atp Efflux

AbstractPannexin1 (PANX1) is a large-pore ATP efflux channel with a broad distribution, which allows the exchange of molecules and ions smaller than 1 kDa between the cytoplasm and extracellular space. In this study, we show that in human macrophages PANX1 expression is upregulated by diverse stimuli that promote pyroptosis, which is reminiscent of the previously reported lipopolysaccharide-induced upregulation of PANX1 during inflammasome activation. To further elucidate the function of PANX1, we propose the full-length human Pannexin1 (hPANX1) model through cryo-electron microscopy (cryo-EM) and molecular dynamics (MD) simulation studies, establishing hPANX1 as a homo-heptamer and revealing that both the N-termini and C-termini protrude deeply into the channel pore funnel. MD simulations also elucidate key energetic features governing the channel that lay a foundation to understand the channel gating mechanism. Structural analyses, functional characterizations, and computational studies support the current hPANX1-MD model, suggesting the potential role of hPANX1 in pyroptosis during immune responses.

scholarly journals C-Terminal Deletions Can Suppress Temperature-Sensitive Mutations and Change Dominance in the Phage Mu Repressor

Genetics ◽  
1996 ◽  
Vol 142 (3) ◽  
pp. 661-672 ◽  
Author(s):  
Jodi L Vogel ◽  
Vincent Geuskens ◽  
Lucie Desmet ◽  
N Patrick Higgins ◽  
Ariane Toussaint
Keyword(s):  
Binding Activity ◽  
Temperature Sensitive ◽  
Dna Binding Activity ◽  
Heat Stable ◽  
C Terminus ◽  
Acid Domain ◽  
Mutant Forms ◽  
Amino Acid Domain

Abstract Mutations in an N-terminal 70-amino acid domain of bacteriophage Mu's repressor cause temperature-sensitive DNA-binding activity. Surprisingly, amber mutations can conditionally correct the heat-sensitive defect in three mutant forms of the repressor gene, cts25 (D43-G), cts62 (R47-Q and cts71 (M28-I), and in the appropriate bacterial host produce a heat-stable Sts phenotype (for survival of temperature shifts). Sts repressor mutants are heat sensitive when in supE or supF hosts and heat resistant when in Sup° hosts. Mutants with an Sts phenotype have amber mutations at one of three codons, Q179, Q187, or Q190. The Sts phenotype relates to the repressor size: in Sup° hosts sts repressors are shorter by seven, 10, or 18 amino acids compared to repressors in supE or supF hosts. The truncated form of the sts62-1 repressor, which lacks 18 residues (Q179–V196), binds Mu operator DNA more stably at 42° in vitro compared to its full-length counterpart (cts62 repressor). In addition to influencing temperature sensitivity, the C-terminus appears to control the susceptibility to in vivo Clp proteolysis by influencing the multimeric structure of repressor.

Inspiring Change through Collaboration:

2014 ◽  
Vol 5 (1) ◽  
pp. 12-21
Author(s):  
Ulla Mäkinen
Keyword(s):  
Full Length ◽  
Real Change

Abstract Since 2007, North Karelia College Outokumpu in Finland, and Cultural College of Petrozavodsk in Russia have collaborated in various educational and artistic exchanges. In 2012, a project called Dancing Whirlpool was launched. In addition to a teacher’s exchange, a joint full-length piece was created together with four choreographer-teachers and nearly thirty students from Outokumpu and Petrozavodsk. The piece toured in Russian and Finnish Karelia. This article reflects on the role of collaboration in multicultural projects, through the lens of the experiences of Dancing Whirlpool. Why is collaboration important for dance students? Can multicultural collaboration invoke real change in our cultures?

Synaptotagmin-1: A Multi-Functional Protein that Mediates Vesicle Docking, Priming, and Fusion

2021 ◽  
Vol 22 ◽  
Author(s):  
Najeeb Ullah ◽  
Ezzouhra El Maaiden ◽  
Md. Sahab Uddin ◽  
Ghulam Md Ashraf
Keyword(s):  
Plasma Membrane ◽  
Secretory Granules ◽  
Secretory Vesicle ◽  
Neuroendocrine Cells ◽  
Snare Complex ◽  
Secretory Vesicles ◽  
Functional Protein ◽  
Vesicle Docking ◽  
Synaptotagmin 1

: The fusion of secretory vesicles with the plasma membrane depends on the assembly of v-SNAREs (VAMP2/synaptobrevin2) and t-SNAREs (SNAP25/syntaxin1) into the SNARE complex. Vesicles go through several upstream steps, referred to as docking and priming, to gain fusion competence. The vesicular protein synaptotagmin-1 (Syt-1) is the principal Ca2+ sensor for fusion in several central nervous system neurons and neuroendocrine cells and part of the docking complex for secretory granules. Syt-1 binds to the acceptor complex such as synaxin1, SNAP-25 on the plasma membrane to facilitate secretory vesicle docking, and upon Ca2+-influx promotes vesicle fusion. This review assesses the role of the Syt-1 protein involved in the secretory vesicle docking, priming, and fusion.

scholarly journals The Cooh-Terminal Domain of Myo2p, a Yeast Myosin V, Has a Direct Role in Secretory Vesicle Targeting

1999 ◽  
Vol 147 (4) ◽  
pp. 791-808 ◽  
Author(s):  
Daniel Schott ◽  
Jackson Ho ◽  
David Pruyne ◽  
Anthony Bretscher
Keyword(s):  
Secretory Vesicle ◽  
Restrictive Temperature ◽  
Secretory Vesicles ◽  
Tail Domain ◽  
Myosin V ◽  
Direct Role ◽  
Rab Protein ◽  
Polarized Delivery ◽  
Actin Cables ◽  
Type V

MYO2 encodes a type V myosin heavy chain needed for the targeting of vacuoles and secretory vesicles to the growing bud of yeast. Here we describe new myo2 alleles containing conditional lethal mutations in the COOH-terminal tail domain. Within 5 min of shifting to the restrictive temperature, the polarized distribution of secretory vesicles is abolished without affecting the distribution of actin or the mutant Myo2p, showing that the tail has a direct role in vesicle targeting. We also show that the actin cable–dependent translocation of Myo2p to growth sites does not require secretory vesicle cargo. Although a fusion protein containing the Myo2p tail also concentrates at growth sites, this accumulation depends on the polarized delivery of secretory vesicles, implying that the Myo2p tail binds to secretory vesicles. Most of the new mutations alter a region of the Myo2p tail conserved with vertebrate myosin Vs but divergent from Myo4p, the myosin V involved in mRNA transport, and genetic data suggest that the tail interacts with Smy1p, a kinesin homologue, and Sec4p, a vesicle-associated Rab protein. The data support a model in which the Myo2p tail tethers secretory vesicles, and the motor transports them down polarized actin cables to the site of exocytosis.

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