Team:Paris/Transduction overview2 transduction

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Signal transduction : Overview

• Introduction
• A. Transduction
  • A.1 ABC transporters
  • A.2 Two Component System
• B. Our strategy
  • B.1 The Fec operon
  • B.2 The trick TCS
• C. Construction

A. Transduction

In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another. Most processes of signal transduction involve ordered sequences of biochemical reactions inside the cell, which are carried out by enzymes and sometimes activated by second messengers, resulting in a signal transduction pathway.

Such processes are usually rapid, lasting on the order of milliseconds in the case of ion flux, or minutes for the activation of proteic cascades, but some can take hours, and even days (as is the case with gene expression), to complete.

We must also refer to the amplification of the signal , in which a relative small stimulus can elicit a large response. It is often du to the increasing numbers of protein ativation implied in the transduction pathways.

blabla grossiste sur la Transduction et de ses possibles façon d'exister. Montrer la présence de ABCT, TCS ou autre truc qui existe, et dire qu'on va détailler les 2 premiers

A.1 ABC transporters

The ABC transporter is a major class of cellular translocation machinery encoded in the largest set of paralogous genes.

The ABC (ATP binding cassette) transporter is one of the active transport systems of the cell, which is widespread in archaea, eubacteria, and eukaryotes. It is also known as the periplasmic binding protein-dependent transport system in Gram-negative bacteria and the binding-lipoprotein-dependent transport system in Gram positive bacteria. The transporter shows a common global organization with three types of molecular components. Typically, it consists of two integral membrane proteins (permeases) each having six transmembrane segments, two peripheral membrane proteins that bind and hydrolyze ATP, and a periplasmic (or lipoprotein) substrate-binding protein. The ATP-binding protein component is the most conserved, the membrane protein component is somewhat less conserved, and the substrate-binding protein component is most divergent in terms of the sequence similarity. The ABC transporters form the largest group of paralogous genes in bacterial and archaeal genomes , and the genes for the three components frequently form an operon.

B.1.1 Uses

ABC transporters utilize the energy of ATP hydrolysis to transport various substrates across cellular membranes. They allow the transport of protein directly into the cytolpasm to activate the transcription.

B.1.2 Advantages/drawbacks

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• advantages:the protein of interest is directly translocated in the cytoplasm and if it is a transcription factor it could activated immediatly the response.
• drawbacks:It is a nutriment uptake system, so basically only small molecules are able to pass thought the membranes and it is a very specific.

A.2 Two-component system

The TCS can be considered as a widely spread class of biosensor knowing that adaptive signal transduction within microbial cells involving a multi-faceted regulated phosphotransfer mechanism that comprises structural rearrangements of sensor histidine kinases upon ligand-binding and phosphorylation-induced conformational changes in response regulators of versatile two-component systems (TCS), arisen early in bacterial evolution.

In most eubacteria, two-component proteins typically constitute *1% of encoded peptides. In pathogenic bacteria they control the expression of important pathogenetic factors, in addition to regulating basic housekeeping functions. The widespread distribution of two-component signal transduction systems in Bacteria and Achaea reflect their biological value as major sensing and response elements to a wide range of environmental insults that are tuned to respond from within milliseconds to hours . Although TCSs are probably the most eficient means of adaptation to conventional stressful stimuli encountered by bacteria during their lifespan, the plasticity of some of these sophisticated systems may contribute to strain-specific cellular processes and to the acquisition of distinct features and phenotypes, particularly in pathogens.

To put the structure in a nutshell : A typical TCS consists of a transmembrane dimeric sensor histidine kinase (HK) and a cytoplasmic cognate response regulator (RR). In gram negative bacteria there is often a Periplasmic Binding Protein which optimize the detection of the molecule localized in the periplasm by a high affinity for the HK after binding the specific molecule. The following scheme shows a typical ABC mechanism :

B.2.1 Uses

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By transferring a packet of molecule synthesize by the donor but not present in the medium, the arrival could activate the transcription of gene of interest.

B.2.2 Advantages/drawbacks

• advantages: This mechanism is dedicated to the transcription of gene under a specific promoter, the difficulty is to find an easily exportable and detectable signal.
• drawbacks: The biosensor are generally sensible to high diffusible molecule for which the vesicles transport is useless.

reference

elles sont ou exactement ?

1. 1995- Cosima Harle & Volkmar Braun - Signal transfer through three compartments transcription initiation of the Escherichia coiferric citrate transport system from the cell surface
2. 2000 - Stock & Goudreau – Two-component signal transduction
3. 2001 - Mishima & Murata - Super-channel in bacteria function and structure of the macromolecule import system mediated by a pit-dependent ABC transporter
4. 2009 - Akyriakidis & Tiligada – signal transduction TCS the AtoSC paradigm
5. 2009 - Tomii & Kanehisa – comparative analysis of ABC transporter