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Depending on the metabolic conditions, the attenuator either stops transcription at that point or allows read-through to the structural gene part of the mRNA and synthesis of the appropriate protein. Attenuation is a regulatory feature found throughout Archaea and Bacteria causing premature termination of transcription. [2]
Translation promotes transcription elongation and regulates transcription termination. Functional coupling between transcription and translation is caused by direct physical interactions between the ribosome and RNA polymerase ("expressome complex"), ribosome-dependent changes to nascent mRNA secondary structure which affect RNA polymerase activity (e.g. "attenuation"), and ribosome-dependent ...
In order for gene expression to proceed, regulatory proteins must bind to the RNA chain and remove the attenuation, which is costly for the cell. [1] [6] In prokaryotes there are two mechanisms of transcription attenuation. These two mechanisms are intrinsic termination and factor-dependent termination.
Photosynthetic reaction centre proteins are main protein components of photosynthetic reaction centres (RCs) of bacteria and plants. They are transmembrane proteins embedded in the chloroplast thylakoid or bacterial cell membrane. Plants, algae, and cyanobacteria have one type of PRC for each of its two photosystems.
This was also significant for being the first 3D crystal structure of any membrane protein complex. Four different subunits were found to be important for the function of the photosynthetic reaction center. The L and M subunits, shown in blue and purple in the image of the structure, both span the lipid bilayer of the plasma membrane.
Cyanobacteria photosystem II, dimer, PDB 2AXT. Photoinhibition occurs in all organisms capable of oxygenic photosynthesis, from vascular plants to cyanobacteria. [14] [15] In both plants and cyanobacteria, blue light causes photoinhibition more efficiently than other wavelengths of visible light, and all wavelengths of ultraviolet light are more efficient than wavelengths of visible light. [14]
The repressor protein binds to the operator in the presence of tryptophan (repressing transcription) and is released from the operon when tryptophan is absent (allowing transcription to proceed). The trp operon additionally uses attenuation to control expression of the operon , a second negative feedback control mechanism.
The chlorophyll a/b-binding protein gene, otherwise known as the CAB gene, is one of the most thoroughly characterized clock-regulated genes in plants. [1] There are a variety of CAB proteins that are derived from this gene family. Studies on Arabidopsis plants have shed light on the mechanisms of biological clocks under the regulation of CAB ...