scholarly journals COPII coat subunit interactions: Sec24p and Sec23p bind to adjacent regions of Sec16p.

1996 ◽  
Vol 7 (11) ◽  
pp. 1815-1823 ◽  
Author(s):  
R E Gimeno ◽  
P Espenshade ◽  
C A Kaiser
Keyword(s):  
Recombinant Proteins ◽  
Ternary Complex ◽  
Membrane Association ◽  
Coat Proteins ◽  
Subunit Interactions ◽  
Central Domain ◽  
C Terminus ◽  
In Vitro Reconstitution ◽  
Two Hybrid

Formation of COPII-coated vesicles at the endoplasmic reticulum (ER) requires assembly onto the membrane of five cytosolic coat proteins, Sec23p, Sec24p, Sec13p, Sec31p, and Sar1p. A sixth vesicle coat component, Sec16p, is tightly associated with the ER membrane and has been proposed to act as a scaffold for membrane association of the soluble coat proteins. We previously showed that Sec23p binds to the C-terminal region of Sec16p. Here we use two-hybrid and coprecipitation assays to demonstrate that the essential COPII protein Sec24p binds to the central region of Sec16p. In vitro reconstitution of binding with purified recombinant proteins demonstrates that the interaction of Sec24p with the central domain of Sec16p does not depend on the presence of Sec23p. However, Sec23p facilitates binding of Sec24p to Sec16p, and the three proteins can form a ternary complex in vitro. Truncations of Sec24p demonstrate that the N-terminal and C-terminal regions of Sec24p display different binding specificities. The C terminus binds to the central domain of Sec16p, whereas the N terminus of Sec24p binds to both the central domain of Sec16p and to Sec23p. These findings define binding to Sec16p as a new function for Sec24p and support the idea that Sec16p organizes assembly of the COPII coat.

scholarly journals SpoVID Guides SafA to the Spore Coat inBacillus subtilis

2001 ◽  
Vol 183 (10) ◽  
pp. 3041-3049 ◽  
Author(s):  
Amanda J. Ozin ◽  
Craig S. Samford ◽  
Adriano O. Henriques ◽  
Charles P. Moran
Keyword(s):  
Direct Interaction ◽  
Spore Coat ◽  
Coat Proteins ◽  
Yeast Two Hybrid System ◽  
Spore Coat Proteins ◽  
Basement Layer ◽  
Two Hybrid ◽  
Spore Coat Protein

ABSTRACT Bacteria assemble complex structures by targeting proteins to specific subcellular locations. The protein coat that encasesBacillus subtilis spores is an example of a structure that requires coordinated targeting and assembly of more than 24 polypeptides. The earliest stages of coat assembly require the action of three morphogenetic proteins: SpoIVA, CotE, and SpoVID. In the first steps, a basement layer of SpoIVA forms around the surface of the forespore, guiding the subsequent positioning of a ring of CotE protein about 75 nm from the forespore surface. SpoVID localizes near the forespore membrane where it functions to maintain the integrity of the CotE ring and to anchor the nascent coat to the underlying spore structures. However, it is not known which spore coat proteins interact directly with SpoVID. In this study we examined the interaction between SpoVID and another spore coat protein, SafA, in vivo using the yeast two-hybrid system and in vitro. We found evidence that SpoVID and SafA directly interact and that SafA interacts with itself. Immunofluorescence microscopy showed that SafA localized around the forespore early during coat assembly and that this localization of SafA was dependent on SpoVID. Moreover, targeting of SafA to the forespore was also dependent on SpoIVA, as was targeting of SpoVID to the forespore. We suggest that the localization of SafA to the spore coat requires direct interaction with SpoVID.

scholarly journals Subforms and In Vitro Reconstitution of the NAD-Reducing Hydrogenase of Alcaligenes eutrophus

1998 ◽  
Vol 180 (5) ◽  
pp. 1023-1029 ◽  
Author(s):  
Christian Massanz ◽  
Silke Schmidt ◽  
Bärbel Friedrich
Keyword(s):  
Alcaligenes Eutrophus ◽  
Nadh:Ubiquinone Oxidoreductase ◽  
Monomeric Form ◽  
Structural Genes ◽  
Wild Type ◽  
Catalytic Function ◽  
C Terminus ◽  
In Vitro Reconstitution ◽  
Reducing Activity

The cytoplasmic, NAD-reducing hydrogenase (SH) of Alcaligenes eutrophus H16 is a heterotetrameric enzyme which contains several cofactors and undergoes a complex maturation during biogenesis. HoxH is the Ni-carrying subunit, and together with HoxY it forms the hydrogenase dimer. HoxF and HoxU represent the flavin-containing diaphorase moiety, which is closely related to NADH:ubiquinone oxidoreductase and mediates NADH oxidation. A variety of mutations were introduced into the four SH structural genes to obtain mutant enzymes composed of monomeric and dimeric forms. A deletion removing most ofhoxF, hoxU, and hoxY led to the expression of a HoxH monomer derivative which was proteolytically processed at the C terminus like the wild-type polypeptide. While the hydrogenase dimer, produced by a strain deleted of hoxF andhoxU, displayed H2-dependent dye-reducing activity, the monomeric form did not mediate the activation of H2, although nickel was incorporated into HoxH. Deletion ofhoxH and hoxY led to the production of HoxFU dimers which displayed NADH:oxidoreductase activity. Mixing the hydrogenase and the diaphorase moieties in vitro reconstituted the structure and catalytic function of the SH holoenzyme.

scholarly journals Genetic Analysis of theEscherichia coliFtsZ·ZipA Interaction in the Yeast Two-hybrid System

2001 ◽  
Vol 276 (15) ◽  
pp. 11980-11987 ◽  
Author(s):  
Steven A. Haney ◽  
Elizabeth Glasfeld ◽  
Cynthia Hale ◽  
David Keeney ◽  
Zhizhen He ◽  
...  
Keyword(s):  
Hybrid System ◽  
Enzyme Linked Immunosorbent Assay ◽  
Wild Type ◽  
Yeast Two Hybrid ◽  
Conserved Sequence ◽  
Yeast Two Hybrid System ◽  
C Terminus ◽  
Two Hybrid

The recruitment of ZipA to the septum by FtsZ is an early, essential step in cell division inEscherichia coli. We have used polymerase chain reaction-mediated random mutagenesis in the yeast two-hybrid system to analyze this interaction and have identified residues within a highly conserved sequence at the C terminus of FtsZ as the ZipA binding site. A search for suppressors of a mutation that causes a loss of interaction (ftsZD373G) identified eight different changes at two residues within this sequence.In vitro, wild type FtsZ interacted with ZipA with a high affinity in an enzyme-linked immunosorbent assay, whereas FtsZD373Gfailed to interact. Two mutant proteins examined restored this interaction significantly.In vivo, the alleles tested are significantly more toxic than the wild typeftsZand cannot complement a deletion. We have shown that a fusion, which encodes the last 70 residues of FtsZ in the two-hybrid system, is sufficient for the interaction with FtsA and ZipA. However, when the wild type sequence is compared with one that encodes FtsZD373G, no interaction was seen with either protein. Mutations surrounding Asp-373 differentially affected the interactions of FtsZ with ZipA and FtsA, indicating that these proteins bind the C terminus of FtsZ differently.

scholarly journals Role of the RNA Polymerase α Subunits in MetR-Dependent Activation of metE and metH: Important Residues in the C-Terminal Domain and Orientation Requirements within RNA Polymerase

2000 ◽  
Vol 182 (19) ◽  
pp. 5539-5550 ◽  
Author(s):  
Paula S. Fritsch ◽  
Mark L. Urbanowski ◽  
George V. Stauffer
Keyword(s):  
Rna Polymerase ◽  
Random Mutagenesis ◽  
Complex Surface ◽  
Α Subunit ◽  
C Terminus ◽  
Distinct Cluster ◽  
In Vitro Reconstitution ◽  
The Difference ◽  
Α Subunits

ABSTRACT Many transcription factors activate by directly interacting with RNA polymerase (RNAP). The C terminus of the RNAP α subunit (αCTD) is a common target of activators. We used both random mutagenesis and alanine scanning to identify αCTD residues that are crucial for MetR-dependent activation of metE and metH. We found that these residues localize to two distinct faces of the αCTD. The first is a complex surface consisting of residues important for α-DNA interactions, activation of both genes (residues 263, 293, and 320), and activation of either metE only (residues 260, 276, 302, 306, 309, and 322) or metH only (residues 258, 264, 290, 294, and 295). The second is a distinct cluster of residues important for metE activation only (residues 285, 289, 313, and 314). We propose that a difference in the location of the MetR binding site for activation at these two promoters accounts for the differences in the residues of α required for MetR-dependent activation. We have designed an in vitro reconstitution-purification protocol that allows us to specifically orient wild-type or mutant α subunits to either the β-associated or the β′-associated position within RNAP (comprising α2, β, β′, and ς subunits). In vitro transcriptions using oriented α RNAP indicate that a single αCTD on either the β- or the β′-associated α subunit is sufficient for MetR activation of metE, while MetR interacts preferentially with the αCTD on the β-associated α subunit at metH. We propose that the different αCTD requirements at these two promoters are due to a combination of the difference in the location of the activation site and limits on the rotational flexibility of the αCTD.

scholarly journals Interaction of the Antiactivator FleN with the Transcriptional Activator FleQ Regulates Flagellar Number inPseudomonas aeruginosa

2001 ◽  
Vol 183 (22) ◽  
pp. 6636-6644 ◽  
Author(s):  
Nandini Dasgupta ◽  
Reuben Ramphal
Keyword(s):  
Binding Protein ◽  
Direct Interaction ◽  
Transcriptional Activator ◽  
Binding Motif ◽  
Yeast Two Hybrid System ◽  
Gtp Binding ◽  
C Terminus ◽  
Enhancer Binding Protein ◽  
Two Hybrid

ABSTRACT Flagellar number in Pseudomonas aeruginosa is controlled by FleN, a putative ATP/GTP binding protein. Disruption offleN results in multiflagellation of the otherwise monoflagellate strains PAK and PAO1 and is associated with a chemotactic defect. We propose that flagellar number is maintained by the antiactivator FleN, which downregulates flagellar genes by binding to their transcriptional activator, FleQ, an enhancer binding protein belonging to the NifA subfamily. In this report we demonstrate direct interaction of FleN and FleQ in the yeast two-hybrid system. Mutagenesis of the putative ATP/GTP binding motif in FleN24K→Q and truncation of FleN at either the N or C terminus abrogates this interaction. FleN does not inhibit the DNA binding ability of FleQ in vitro, thus indicating that it probably utilizes another mechanism(s) to serve as a FleQ antiactivator.

scholarly journals Key driving forces in the biosynthesis of autoinducing peptides required for staphylococcal virulence

2015 ◽  
Vol 112 (34) ◽  
pp. 10679-10684 ◽  
Author(s):  
Boyuan Wang ◽  
Aishan Zhao ◽  
Richard P. Novick ◽  
Tom W. Muir
Keyword(s):  
Quorum Sensing ◽  
Driving Forces ◽  
Side Chain ◽  
Accessory Gene ◽  
Accessory Gene Regulator ◽  
C Terminus ◽  
In Vitro Reconstitution ◽  
Intimate Link ◽  
Autoinducing Peptides

Staphylococci produce autoinducing peptides (AIPs) as quorum-sensing signals that regulate virulence. These AIPs feature a thiolactone macrocycle that connects the peptide C terminus to the side chain of an internal cysteine. AIPs are processed from ribosomally synthesized precursors [accessory gene regulator D (AgrD)] through two proteolytic events. Formation of the thiolactone is coupled to the first of these and involves the activity of the integral membrane protease AgrB. This step is expected to be thermodynamically unfavorable, and therefore, it is unclear how AIP-producing bacteria produce sufficient amounts of the thiolactone-containing intermediate to drive quorum sensing. Herein, we present the in vitro reconstitution of the AgrB-dependent proteolysis of an AgrD precursor from Staphylococcus aureus. Our data show that efficient thiolactone production is driven by two unanticipated features of the system: (i) membrane association of the thiolactone-containing intermediate, which stabilizes the macrocycle, and (ii) rapid degradation of the C-terminal proteolysis fragment AgrDC, which affects the reaction equilibrium position. Cell-based studies confirm the intimate link between AIP production and intracellular AgrDC levels. Thus, our studies explain the chemical principles that drive AIP production, including uncovering a hitherto unknown link between quorum sensing and peptide turnover.

scholarly journals ADP-Ribosylation Factor 1 (ARF1) Regulates Recruitment of the AP-3 Adaptor Complex to Membranes

1998 ◽  
Vol 142 (2) ◽  
pp. 391-402 ◽  
Author(s):  
Chean Eng Ooi ◽  
Esteban C. Dell'Angelica ◽  
Juan S. Bonifacino
Keyword(s):  
Membrane Trafficking ◽  
Brefeldin A ◽  
Membrane Association ◽  
Coat Proteins ◽  
Nucleotide Exchange ◽  
Membrane Recruitment ◽  
Adp Ribosylation ◽  
Adp Ribosylation Factor

Small GTP-binding proteins such as ADP- ribosylation factor 1 (ARF1) and Sar1p regulate the membrane association of coat proteins involved in intracellular membrane trafficking. ARF1 controls the clathrin coat adaptor AP-1 and the nonclathrin coat COPI, whereas Sar1p controls the nonclathrin coat COPII. In this study, we demonstrate that membrane association of the recently described AP-3 adaptor is regulated by ARF1. Association of AP-3 with membranes in vitro was enhanced by GTPγS and inhibited by brefeldin A (BFA), an inhibitor of ARF1 guanine nucleotide exchange. In addition, recombinant myristoylated ARF1 promoted association of AP-3 with membranes. The role of ARF1 in vivo was examined by assessing AP-3 subcellular localization when the intracellular level of ARF1-GTP was altered through overexpression of dominant ARF1 mutants or ARF1- GTPase-activating protein (GAP). Lowering ARF1-GTP levels resulted in redistribution of AP-3 from punctate membrane-bound structures to the cytosol as seen by immunofluorescence microscopy. In contrast, increasing ARF1-GTP levels prevented redistribution of AP-3 to the cytosol induced by BFA or energy depletion. Similar experiments with mutants of ARF5 and ARF6 showed that these other ARF family members had little or no effect on AP-3. Taken together, our results indicate that membrane recruitment of AP-3 is promoted by ARF1-GTP. This finding suggests that ARF1 is not a regulator of specific coat proteins, but rather is a ubiquitous molecular switch that acts as a transducer of diverse signals influencing coat assembly.

scholarly journals Kinectin Is a Key Effector of RhoG Microtubule-Dependent Cellular Activity

2001 ◽  
Vol 21 (23) ◽  
pp. 8022-8034 ◽  
Author(s):  
E. Vignal ◽  
A. Blangy ◽  
M. Martin ◽  
C. Gauthier-Rouvière ◽  
P. Fort
Keyword(s):  
Time Lapse ◽  
Yeast Two Hybrid ◽  
Downstream Signaling ◽  
C Terminus ◽  
Rho Family ◽  
Conventional Kinesin ◽  
Dependent Pathway ◽  
Two Hybrid ◽  
Lysosomal Transport

ABSTRACT RhoG is a member of the Rho family of GTPases that activates Rac1 and Cdc42 through a microtubule-dependent pathway. To gain understanding of RhoG downstream signaling, we performed a yeast two-hybrid screen from which we identified kinectin, a 156-kDa protein that binds in vitro to conventional kinesin and enhances microtubule-dependent kinesin ATPase activity. We show that RhoGGTP specifically interacts with the central domain of kinectin, which also contains a RhoA binding domain in its C terminus. Interaction was confirmed by coprecipitation of kinectin with active RhoGG12V in COS-7 cells. RhoG, kinectin, and kinesin colocalize in REF-52 and COS-7 cells, mainly in the endoplasmic reticulum but also in lysosomes. Kinectin distribution in REF-52 cells is modulated according to endogenous RhoG activity. In addition, by using injection of anti-kinectin antibodies that challenge RhoG-kinectin interaction or by blocking anti-kinesin antibodies, we show that RhoG morphogenic activity relies on kinectin interaction and kinesin activity. Finally, kinectin overexpression elicits Rac1- and Cdc42-dependent cytoskeletal effects and switches cells to a RhoA phenotype when RhoG activity is inhibited or microtubules are disrupted. The functional links among RhoG, kinectin, and kinesin are further supported by time-lapse videomicroscopy of COS-7 cells, which showed that the microtubule-dependent lysosomal transport is facilitated by RhoG activation or kinectin overexpression and is severely stemmed upon RhoG inhibition. These data establish that kinectin is a key mediator of microtubule-dependent RhoG activity and suggest that kinectin also mediates RhoG- and RhoA-dependent antagonistic pathways.

scholarly journals P1 ParB Domain Structure Includes Two Independent Multimerization Domains

1999 ◽  
Vol 181 (19) ◽  
pp. 5898-5908 ◽  
Author(s):  
Jennifer A. Surtees ◽  
Barbara E. Funnell
Keyword(s):  
Amino Acids ◽  
Domain Structure ◽  
Cross Linking ◽  
Yeast Two Hybrid ◽  
Yeast Two Hybrid System ◽  
C Terminus ◽  
Self Association ◽  
Two Hybrid ◽  
Chemical Cross Linking

ABSTRACT ParB is one of two P1-encoded proteins that are required for active partition of the P1 prophage in Escherichia coli. To probe the native domain structure of ParB, we performed limited proteolytic digestions of full-length ParB, as well as of several N-terminal and C-terminal deletion fragments of ParB. The C-terminal 140 amino acids of ParB form a very trypsin-resistant domain. In contrast, the N terminus is more susceptible to proteolysis, suggesting that it forms a less stably folded domain or domains. Because native ParB is a dimer in solution, we analyzed the ability of ParB fragments to dimerize, using both the yeast two-hybrid system and in vitro chemical cross-linking of purified proteins. These studies revealed that the C-terminal 59 amino acids of ParB, a region within the protease-resistant domain, are sufficient for dimerization. Cross-linking and yeast two-hybrid experiments also revealed the presence of a second self-association domain within the N-terminal half of ParB. The cross-linking data also suggest that the C terminus is inhibitory to multimerization through the N-terminal domain in vitro. We propose that the two multimerization domains play distinct roles in partition complex formation.

scholarly journals Protein Interaction between Ameloblastin and Proteasome Subunit α Type 3 Can Facilitate Redistribution of Ameloblastin Domains within Forming Enamel

2015 ◽  
Vol 290 (34) ◽  
pp. 20661-20673 ◽  
Author(s):  
Shuhui Geng ◽  
Shane N. White ◽  
Michael L. Paine ◽  
Malcolm L. Snead
Keyword(s):  
Matrix Proteins ◽  
Protein Distribution ◽  
Proteasome Subunit ◽  
C Terminus ◽  
The Matrix ◽  
Lateral Margins ◽  
Type 3 ◽  
Two Hybrid

Enamel is a bioceramic tissue composed of thousands of hydroxyapatite crystallites aligned in parallel within boundaries fabricated by a single ameloblast cell. Enamel is the hardest tissue in the vertebrate body; however, it starts development as a self-organizing assembly of matrix proteins that control crystallite habit. Here, we examine ameloblastin, a protein that is initially distributed uniformly across the cell boundary but redistributes to the lateral margins of the extracellular matrix following secretion thus producing cell-defined boundaries within the matrix and the mineral phase. The yeast two-hybrid assay identified that proteasome subunit α type 3 (Psma3) interacts with ameloblastin. Confocal microscopy confirmed Psma3 co-distribution with ameloblastin at the ameloblast secretory end piece. Co-immunoprecipitation assay of mouse ameloblast cell lysates with either ameloblastin or Psma3 antibody identified each reciprocal protein partner. Protein engineering demonstrated that only the ameloblastin C terminus interacts with Psma3. We show that 20S proteasome digestion of ameloblastin in vitro generates an N-terminal cleavage fragment consistent with the in vivo pattern of ameloblastin distribution. These findings suggest a novel pathway participating in control of protein distribution within the extracellular space that serves to regulate the protein-mineral interactions essential to biomineralization.

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