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Interaction Domains (interaction + domain)
Selected AbstractsDeletion of Brca2 exon 27 causes hypersensitivity to DNA crosslinks, chromosomal instability, and reduced life span in miceGENES, CHROMOSOMES AND CANCER, Issue 4 2003Greg Donoho The Brca2 tumor-suppressor gene contributes to genomic stability, at least in part by a role in homologous recombinational repair. BRCA2 protein is presumed to function in homologous recombination through interactions with RAD51. Both exons 11 and 27 of Brca2 code for domains that interact with RAD51; exon 11 encodes eight BRC motifs, whereas exon 27 encodes a single, distinct interaction domain. Deletion of all RAD51-interacting domains causes embryonic lethality in mice. A less severe phenotype is seen with BRAC2 truncations that preserve some, but not all, of the BRC motifs. These mice can survive beyond weaning, but are runted and infertile, and die very young from cancer. Cells from such mice show hypersensitivity to some genotoxic agents and chromosomal instability. Here, we have analyzed mice and cells with a deletion of only the RAD51-interacting region encoded by exon 27. Mice homozygous for this mutation (called brca2lex1) have a shorter life span than that of control littermates, possibly because of early onsets of cancer and sepsis. No other phenotype was observed in these animals; therefore, the brca2lex1 mutation is less severe than truncations that delete some BRC motifs. However, at the cellular level, the brca2lex1 mutation causes reduced viability, hypersensitivity to the DNA interstrand crosslinking agent mitomycin C, and gross chromosomal instability, much like more severe truncations. Thus, the extreme carboxy-terminal region encoded by exon 27 is important for BRCA2 function, probably because it is required for a fully functional interaction between BRCA2 and RAD51. © 2003 Wiley-Liss, Inc. [source] The PAK family kinase Cla4 is required for budding and morphogenesis in Ustilago maydisMOLECULAR MICROBIOLOGY, Issue 2 2004Leonora Leveleki Summary The phytopathogenic basidiomycete Ustilago maydis displays a dimorphic switch between budding growth of haploid cells and filamentous growth of the dikaryon. In a screen for mutants affected in morphogenesis and cytokinesis, we identified the serine/threonine protein kinase Cla4, a member of the family of p21-activated kinases (PAKs). Cells, in which cla4 has been deleted, are viable but they are unable to bud properly. Instead, cla4 mutant cells grow as branched septate hyphae and divide by contraction and fission at septal cross walls. Delocalized deposition of chitinous cell wall material along the cell surface is observed in cla4 mutant cells. Deletion of the Cdc42/Rac1 interaction domain (CRIB) results in a constitutive active Cla4 kinase, whose expression is lethal for the cell. cla4 mutant cells are unable to induce pathogenic development in plants and to display filamentous growth in a mating reaction, although they are still able to secrete pheromone and to undergo cell fusion with wild-type cells. We propose that Cla4 is involved in the regulation of cell polarity during budding and filamentation. [source] Delineation of pilin domains required for bacterial association into microcolonies and intestinal colonization by Vibrio choleraeMOLECULAR MICROBIOLOGY, Issue 4 2000Thomas J. Kirn The toxin-co-regulated pilus (TCP), a type 4 pilus that is expressed by epidemic strains of Vibrio cholerae O1 and O139, is required for colonization of the human intestine. The TCP structure is assembled as a polymer of repeating subunits of TcpA pilin that form long fibres, which laterally associate into bundles. Previous passive immunization studies have suggested that the C-terminal region of TcpA is exposed on the surface of the pilus fibre and has a critical role in mediating the colonization functions of TCP. In the present study, we have used site-directed mutagenesis to delineate two domains within the C-terminal region that contribute to TCP structure and function. Alterations in the first domain, termed the structural domain, result in altered pilus stability or morphology. Alterations in the second domain, termed the interaction domain, affect colonization and/or infection by CTX-bacteriophage without affecting pilus morphology. In vitro and in vivo analyses of the tcpA mutants revealed that a major function of TCP is to mediate bacterial interaction through direct pilus,pilus contact required for microcolony formation and productive intestinal colonization. The importance of this function is supported by the finding that intragenic suppressor mutations that restore colonization ability to colonization-deficient mutants simultaneously restore pilus-mediated bacterial interactions. The alterations resulting from the suppressor mutations also provide insight into the molecular interactions between pilin subunits within and between pilus fibres. [source] Conflict and support interactions in marriage: An analysis of couples' interactive behavior and on-line cognitionPERSONAL RELATIONSHIPS, Issue 1 2005Lesley L. Verhofstadt The present study examined the similarities and differences in couples' interactive behavior and interaction-based cognition that emerged in comparisons of conflict and support interactions in marriage. In a laboratory experiment, 53 couples were randomly assigned to the conditions of a 2 (type of interaction: conflict vs. support) × 2 (initiator of interaction: man vs. woman) factorial design. Partners provided questionnaire data and participated in a joint interaction and video review task. The data revealed substantial behavioral similarities (i.e., some classes of validation/facilitation behaviors and neutral problem-solving behaviors) as well as behavioral differences (i.e., some classes of invalidation/oppositional behaviors) between conflict and support interactions, controlling for levels of marital satisfaction. Partners' interaction-based cognition (e.g., feeling understood, satisfied) was especially affected by classes of validation/facilitation behaviors and was consistently related to marital satisfaction. In broad terms, the impact of a particular behavior on partners' ongoing cognition did not depend on the interaction domain (conflict vs. support) in which the behavior occurred. [source] Modulation of protein kinase C by curcumin; inhibition and activation switched by calcium ionsBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2007Y A Mahmmoud Background and purpose: Previous studies have identified the natural polyphenol curcumin as a protein kinase C (PKC) inhibitor. In contrast, we found significant stimulation of PKC activity following curcumin treatment. Thus, the mechanism of curcumin interaction with PKC was investigated. Experimental approach: We employed phosphorylation assays in the presence of soluble or membrane-bound PKC substrates, followed by SDS,PAGE, autoradiography and phosphorylation intensity measurements. Key results: Curcumin inhibited PKC in the absence of membranes whereas stimulation was observed in the presence of membranes. Further analysis indicated that curcumin decreased PKC activity by competition with Ca2+ stimulation of the kinase, resulting in inhibition of activity at lower Ca2+ concentrations and stimulation at higher Ca2+ concentrations. The role of the membrane is likely to be facilitation of Ca2+ -binding to the kinase, thus relieving the curcumin inhibition observed at limited Ca2+ concentrations. Curcumin was found to mildly stimulate the catalytic subunit of PKC, which does not require Ca2+ for activation. In addition, studies on Ca2+ -independent PKC isoforms as well as another curcumin target (the sarcoplasmic reticulum Ca2+ -ATPase) confirmed a correlation between Ca2+ concentration and the curcumin effects. Conclusions and Implications: Curcumin competes with Ca2+ for the regulatory domain of PKC, resulting in a Ca2+ -dependent dual effect on the kinase. We propose that curcumin interacts with the Ca2+ -binding domains in target proteins. To our knowledge, this is the first study that defines an interaction domain for curcumin, and provides a rationale for the broad specificity of this polyphenol as a chemopreventive drug. British Journal of Pharmacology (2007) 150, 200,208. doi:10.1038/sj.bjp.0706970 [source] Scaffolding proteins organize multimolecular protein complexes for sensory signal transductionEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2001Armin Huber Abstract Scaffolding proteins composed of protein,protein interaction domains have emerged as organizers of multiprotein complexes in diverse cellular compartments, including neuronal synapses, cell,cell junctions of epithelial cells, and the stimulus perceiving structures of sensory neurons. This review focuses on the INAD-assembled signalling complex of Drosophila photoreceptors, which organizes key components of the phototransduction cascade into a multiprotein signal transduction unit. The structure, the physiological consequences, and the assembly and targeting of the members of the INAD signalling complex will be described. In addition, the existence of signalling complexes in vertebrate photoreceptors, olfactory neurons and mechanosensitive hair cells will be discussed. [source] Death-associated protein kinase (DAPK) and signal transduction: additional roles beyond cell deathFEBS JOURNAL, Issue 1 2010Yao Lin Death-associated protein kinase (DAPK) is a stress-regulated protein kinase that mediates a range of processes, including signal-induced cell death and autophagy. Although the kinase domain of DAPK has a range of substrates that mediate its signalling, the additional protein interaction domains of DAPK are relatively ill defined. This review will summarize our current knowledge of the DAPK interactome, the use of peptide aptamers to define novel protein,protein interaction motifs, and how these new protein,protein interactions give insight into DAPK functions in diverse cellular processes, including growth factor signalling, the regulation of autophagy, and its emerging role in the regulation of immune responses. [source] SMC Proteins at the Crossroads of Diverse Chromosomal ProcessesIUBMB LIFE, Issue 12 2003Rolf Jessberger Abstract How should a protein be designed to serve in processes as diverse as chromosome condensation, sister chromatid cohesion, DNA recombination, gene dosage regulation, and perhaps even gene silencing or transcriptional regulation - which occur in both mitosis and meiosis? Such a protein or protein complex needs to bear DNA interaction domains, it needs the capacity to use energy to move DNA, it needs to enter into highly specific protein interactions, it needs to be large enough to link two DNA molecules, it needs to be of sufficient flexibility to cope with different types of chromatin structure, yet it also needs to be rigid enough to pull, push or enclose DNA. SMC proteins fulfill these requirements and form the core units of high molecular weight complexes that act in all those processes, and are essential for some of them. SMC stands for 'Structural Maintenance of Chromosomes', although SMC proteins are not static scaffold proteins merely providing support for a particular chromosome structure. SMC proteins are rather highly dynamic actors, that generate and modulate chromosome structures, affecting a plethora of biological processes. IUBMB Life, 55: 643-652, 2003 [source] The interaction of KCTD1 with transcription factor AP-2, inhibits its transactivation,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2009Xiaofeng Ding Abstract AP-2 is a transcription factor implicated in mammalian development, cell proliferation, apoptosis, and carcinogenesis. To identify potential AP-2,-interacting partners, a yeast two-hybrid screen was performed in human brain cDNA library. One of the identified clones encodes potassium channel tetramerization domain-containing 1 (KCTD1). We demonstrated the novel KCTD1,AP-2, interaction in vitro by GST pull-down assays and in vivo by co-immunoprecipitation assays and mapped the interaction domains to the N-termini of both proteins. In addition, we observed that the two proteins were completely co-localized in the nuclei of mammalian cells. Transient transfection assays using four promoters containing AP-2-binding sites confirmed that KCTD1 significantly repressed AP-2,-mediated transactivation through the BTB domain, whereas KCTD1 siRNA strongly relieved KCTD1-mediated repression of AP-2, transcriptional activity, and other BTB domain proteins such as PDIP1, KCTD10, and TNFAIP1 did not markedly inhibit the transcriptional activity of AP-2,, suggesting that KCTD1 specifically acts as a negative regulator of AP-2,. Finally, we found that KCTD1 interacted with three major members of the AP-2 family and inhibited their transcriptional activities. Taken together, our results indicate the novel function of KCTD1 as the transcriptional repressor for AP-2 family, especially for AP-2,. J. Cell. Biochem. 106: 285,295, 2009. © 2008 Wiley-Liss, Inc. [source] 4-Fluoroproline derivative peptides: effect on PPII conformation and SH3 affinityJOURNAL OF PEPTIDE SCIENCE, Issue 7 2006Paolo Ruzza Abstract Eukaryotic signal transduction involves the assembly of transient protein,protein complexes mediated by modular interaction domains. Specific Pro-rich sequences with the consensus core motif PxxP adopt the PPII helix conformation upon binding to SH3 domains. For short Pro-rich peptides, little or no ordered secondary structure is usually observed before binding interactions. The association of a Pro-rich peptide with the SH3 domain involves unfavorable binding entropy due to the loss of rotational freedom on forming the PPII helix. With the aim of stabilizing the PPII helix conformation in the Pro-rich HPK1 decapeptide PPPLPPKPKF (P2), a series of P2 analogues was prepared, in which specific Pro positions were alternatively occupied by 4(S)- or 4(R)-4-fluoro- L -proline. The interactions of these peptides with the SH3 domain of the HPK1-binding partner HS1 were quantitatively analyzed by the NILIA-CD approach. A CD thermal analysis of the P2 analogues was performed to assess their propensity to adopt the PPII helix conformation. Contrary to our expectations, the Kd values of the analogues were lower than that of the parent peptide P2. These results clearly show that the induction of a stable PPII helix conformation in short Pro-rich peptides is not sufficient to increase their affinity toward the SH3 domain and that the effect of 4-fluoroproline strongly depends on the position of this residue in the sequence and the chirality of the substituent in the pyrrolidine ring. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd. [source] Characterization of the interaction partners of secreted proteins and chaperones of Shigella flexneriMOLECULAR MICROBIOLOGY, Issue 4 2001Anne-Laure Page The type III secretion (TTS) system of Gram-negative pathogenic bacteria is composed of proteins that assemble into the TTS machinery, proteins that are secreted by this machinery and specific chaperones that are required for storage and sometimes secretion of these proteins. Many sequential protein interactions are involved in the TTS pathway to deliver effector proteins to host cells. We used the yeast two-hybrid system to investigate the interaction partners of the Shigella flexneri effectors and chaperones. Libraries of preys containing random fusions with fragments of the TTS proteins were screened using effectors and chaperones as baits. Interactions between the effectors IpaB and IpaC and their chaperone IpgC were detected by this method, and interaction domains were identified. Using a His-tagged IpgC protein to co-purify truncated IpaB and IpaC proteins, we showed that the chaperone-binding domain was unique and located in the N-terminus of these proteins. This domain was not required for the secretion of recombinant proteins but was involved in the stability of IpaC and instability of IpaB. Homotypic interactions were identified with the baits IpaA, IpaB and IpaC. Interactions between effectors and components of the TTS machinery were also selected that might give insights into regulation of the TTS process. [source] Crystal structures of oxidized and reduced forms of human mitochondrial thioredoxin 2PROTEIN SCIENCE, Issue 10 2005Aude Smeets ASK1, apoptosis signal-regulating kinase 1; TXN, thioredoxin; hTXN1, human cytosolic/nuclear thioredoxin 1; hTXN2, human mitochondrial thioredoxin 2; hPRDX5, human peroxiredoxin 5. Gene symbols in this article follow standard nomenclature defined by the Human Genome Organization Nomenclature Committee (http://www.gene.ucl.ac.uk/nomenclature/). For this reason TXN is used instead of the commonly used Trx for designating thioredoxin in the literature. Abstract Mammalian thioredoxin 2 is a mitochondrial isoform of highly evolutionary conserved thioredoxins. Thioredoxins are small ubiquitous protein,disulfide oxidoreductases implicated in a large variety of biological functions. In mammals, thioredoxin 2 is encoded by a nuclear gene and is targeted to mitochondria by a N-terminal mitochondrial presequence. Recently, mitochondrial thioredoxin 2 was shown to interact with components of the mitochondrial respiratory chain and to play a role in the control of mitochondrial membrane potential, regulating mitochondrial apoptosis signaling pathway. Here we report the first crystal structures of a mammalian mitochondrial thioredoxin 2. Crystal forms of reduced and oxidized human thioredoxin 2 are described at 2.0 and 1.8 Å resolution. Though the folding is rather similar to that of human cytosolic/nuclear thioredoxin 1, important differences are observed during the transition between the oxidized and the reduced states of human thioredoxin 2, compared with human thioredoxin 1. In spite of the absence of the Cys residue implicated in dimer formation in human thioredoxin 1, dimerization still occurs in the crystal structure of human thioredoxin 2, mainly mediated by hydrophobic contacts, and the dimers are associated to form two-dimensional polymers. Interestingly, the structure of human thioredoxin 2 reveals possible interaction domains with human peroxiredoxin 5, a substrate protein of human thioredoxin 2 in mitochondria. [source] Functional importance of conserved domains in the flowering-time gene CONSTANS demonstrated by analysis of mutant alleles and transgenic plantsTHE PLANT JOURNAL, Issue 6 2001Frances Robson Summary CONSTANS promotes flowering of Arabidopsis in response to long-day conditions. We show that CONSTANS is a member of an Arabidopsis gene family that comprises 16 other members. The CO-Like proteins encoded by these genes contain two segments of homology: a zinc finger containing region near their amino terminus and a CCT (CO, CO-Like, TOC1) domain near their carboxy terminus. Analysis of seven classical co mutant alleles demonstrated that the mutations all occur within either the zinc finger region or the CCT domain, confirming that the two regions of homology are important for CO function. The zinc fingers are most similar to those of B-boxes, which act as protein,protein interaction domains in several transcription factors described in animals. Segments of CO protein containing the CCT domain localize GFP to the nucleus, but one mutation that affects the CCT domain delays flowering without affecting the nuclear localization function, suggesting that this domain has additional functions. All eight co alleles, including one recovered by pollen irradiation in which DNA encoding both B-boxes is deleted, are shown to be semidominant. This dominance appears to be largely due to a reduction in CO dosage in the heterozygous plants. However, some alleles may also actively delay flowering, because overexpression from the CaMV 35S promoter of the co-3 allele, that has a mutation in the second B-box, delayed flowering of wild-type plants. The significance of these observations for the role of CO in the control of flowering time is discussed. [source] | ||||||||||||||||