A conserved protein interaction network involving the yeast MAP kinases Fus3 and Kss1

The Saccharomyces cerevisiae mitogen-activated protein kinases (MAPKs) Fus3 and Kss1 bind to multiple regulators and substrates. We show that mutations in a conserved docking site in these MAPKs (the CD/7m region) disrupt binding to an important subset of their binding partners, including the Ste7 MAPK kinase, the Ste5 adaptor/scaffold protein, and the Dig1 and Dig2 transcriptional repressors. Supporting the possibility that Ste5 and Ste7 bind to the same region of the MAPKs, they partially competed for Fus3 binding. In vivo, some of the MAPK mutants displayed reduced Ste7-dependent phosphorylation, and all of them exhibited multiple defects in mating and pheromone response. The Kss1 mutants were also defective in Kss1-imposed repression of Ste12. We conclude that MAPKs contain a structurally and functionally conserved docking site that mediates an overall positively acting network of interactions with cognate docking sites on their regulators and substrates. Key features of this interaction network appear to have been conserved from yeast to humans

Membrane Recruitment of Scaffold Proteins Drives Specific Signaling

Cells must give the right response to each stimulus they receive. Scaffolding, a signaling process mediated by scaffold proteins, participates in the decoding of the cues by specifically directing signal transduction. The aim of this paper is to describe the molecular mechanisms of scaffolding, i.e. the principles by which scaffold proteins drive a specific response of the cell. Since similar scaffold proteins are found in many species, they evolved according to the purpose of each organism. This means they require adaptability. In the usual description of the mechanisms of scaffolding, scaffold proteins are considered as reactors where molecules involved in a cascade of reactions are simultaneously bound with the right orientation to meet and interact. This description is not realistic: (i) it is not verified by experiments and (ii) timing and orientation constraints make it complex which seems to contradict the required adaptability. A scaffold protein, Ste5, is used in the MAPK pathway of Saccharomyces Cerevisiae for the cell to provide a specific response to stimuli. The massive amount of data available for this pathway makes it ideal to investigate the actual mechanisms of scaffolding. Here, a complete treatment of the chemical reactions allows the computation of the distributions of all the proteins involved in the MAPK pathway when the cell receives various cues. These distributions are compared to several experimental results. It turns out that the molecular mechanisms of scaffolding are much simpler and more adaptable than previously thought in the reactor model. Scaffold proteins bind only one molecule at a time. Then, their membrane recruitment automatically drives specific, amplified and localized signal transductions. The mechanisms presented here, which explain how the membrane recruitment of a protein can produce a drastic change in the activity of cells, are generic and may be commonly used in many biological processes

Computational Prediction and Experimental Verification of New MAP Kinase Docking Sites and Substrates Including Gli Transcription Factors

In order to fully understand protein kinase networks, new methods are needed to identify regulators and substrates of kinases, especially for weakly expressed proteins. Here we have developed a hybrid computational search algorithm that combines machine learning and expert knowledge to identify kinase docking sites, and used this algorithm to search the human genome for novel MAP kinase substrates and regulators focused on the JNK family of MAP kinases. Predictions were tested by peptide array followed by rigorous biochemical verification with in vitro binding and kinase assays on wild-type and mutant proteins. Using this procedure, we found new ‘D-site’ class docking sites in previously known JNK substrates (hnRNP-K, PPM1J/PP2Czeta), as well as new JNK-interacting proteins (MLL4, NEIL1). Finally, we identified new D-site-dependent MAPK substrates, including the hedgehog-regulated transcription factors Gli1 and Gli3, suggesting that a direct connection between MAP kinase and hedgehog signaling may occur at the level of these key regulators. These results demonstrate that a genome-wide search for MAP kinase docking sites can be used to find new docking sites and substrates

Metabolic profiling identifies trehalose as an abundant and diurnally fluctuating metabolite in the microalga Ostreococcus tauri

© 2017, The Author(s).Introduction: The picoeukaryotic alga Ostreococcus tauri (Chlorophyta) belongs to the widespread group of marine prasinophytes. Despite its ecological importance, little is known about the metabolism of this alga. Objectives: In this work, changes in the metabolome were quantified when O. tauri was grown under alternating cycles of 12 h light and 12 h darkness. Methods: Algal metabolism was analyzed by gas chromatography-mass spectrometry. Using fluorescence-activated cell sorting, the bacteria associated with O. tauri were depleted to below 0.1% of total cells at the time of metabolic profiling. Results: Of 111 metabolites quantified over light–dark cycles, 20 (18%) showed clear diurnal variations. The strongest fluctuations were found for trehalose. With an intracellular concentration of 1.6 mM in the dark, this disaccharide was six times more abundant at night than during the day. This fluctuation pattern of trehalose may be a consequence of starch degradation or of the synchronized cell cycle. On the other hand, maltose (and also sucrose) was below the detection limit (~10 μM). Accumulation of glycine in the light is in agreement with the presence of a classical glycolate pathway of photorespiration. We also provide evidence for the presence of fatty acid methyl and ethyl esters in O. tauri. Conclusions: This study shows how the metabolism of O. tauri adapts to day and night and gives new insights into the configuration of the carbon metabolism. In addition, several less common metabolites were identified

Study Faktor-faktor yang Mempengaruhi Perilaku Pengobatan Sendiri

Perilaku pengobatan sendiri merupakan salah satu perilaku kesehatan. Dewasa ini hampir sebagian masyarakat lebih memilih melakukan pengobatan sendiri menggunakan obat bebas terbatas dari pada harus pergi berobat ke tenaga kesehatan atau Dokter. Hal ini di pengaruhi oleh berbagai faktor antara lain faktor pendidikan, tempat tinggal, biaya, usia, pekerjaan, dan lama sakit. Tujuan penelitian adalah mengidentifikasi faktor-faktor pengobatan sendiri di desa prambon.Penelitian ini menggunakan metode deskriptif yaitu metode penelitian yang dilakukan dengan membuat gambaran atau deskripsi tentang suatu keaadan secara obyektif dengan desain penelitian pendekatan survey di desa Prambon kecamatan Soko kabupaten Tuban pada bulan juni sampai dengan juli 2010. Pengambilan sampling secara Non Probability Sampling menggunakan tehnik Purposive Sampling dengan jumlah responden 200 orang. Data yang didapatkan dari kuesioner kemudian ditabulasikan serta dikelompokkan sesuai diagram pie.Hasil penelitian menunjukkan bahwa perilaku pengobatan sendiri dipengaruhi oleh faktor pendidikan rendah SD 185 responden (92,5%), tempat tinggal berjarak lebih dari 5 km 180 responden (90%), biaya pengobatan kurang dari Rp. 2500,- 125 responden (62,5%), usia lebih dari 45 tahun 128 responden (64%), pekerjaan untuk orang tidak bekerja 130 responden (65%), dan lama menderita penyakit kronis 110 responden (55%).Pada penelitian ini dapat disimpulkan bahwa faktor yang mempengaruhi perilaku pengobatan sendiri adalah faktor pendidikan, tempat tinggal, biaya, usia, pekerjaan, dan lama sakit. Oleh karena itu diharapkan pada masyarakat untuk melakukan pengobatan ke pelayanan kesehatan yang ada untuk menghindari dampak negatif yang ditimbulkan dari pengobatan sendiri yang tidak tepat, meminta petunjuk tentang pengobatan sendiri ke petugas kesehatan