Bioluminescence Flashcards
(15 cards)
What
Biologically produced light
Enzymatic reaction
Luciferin (substrate) + luciferase (enzyme)
Oxidation reactions
Broad range of organisms
Functions
Repulsion
Communication
Attraction of prey
Hunting
Defense
Camo
Reproduction
Origins and evolution
Molecular diversity
Multiple convergent evolution
Antioxidant protection in the first place
Bioluminescence of Aequorea Victoria
Aequorion: enzyme substrate complex of apoaequorin (enzyme) and coelenterazine (substrate)
Formed in an oxidation reaction
Ca2+ induces a conformational change of aequorin, resulting in a break down of the enzyme substrate complex and release of photons
Green fluorescent protein
Located in the geometric centre of the molecule
Formed by the tripeptide Ser-Tyr-Gly
Autocatalytics reaction in presence of O
Genetic coding of colour of fluorescence
GFP is monomeric in solution
Acropora pulchra
Blue colour, purple-blue chromoproteins
GFP-like proteins, homolog to anthozoans fluorescent proteins
Bacterial bioluminescence
Oxidation of a flavin mononucleotide
Use of a long chain aldehyde
Recycling of the compounds requires energy
Lux genes
Genes for the bioluminescent system are organised into two operons
Operon
Functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter
Genes are transcribed together into an mRNA strand
The RNA is either translated together or undergoes trans-splicing to create multiple mRNAs that are translated separately.
Right lux operon
Genes for bacterial luciferase subunits
Genes for the fatty acid reductase polypeptides
Luxl, the gene responsible for synthesizing the autoinducer
LuxG, unknown function, but it hasn’t been indentified in terrestrial luminescent bacteria
Left Operon
Expression of luxR, receptor protein for the autoinducer
Two genes are not part of the operons
Rib is a key component of the flavin mononucleotide biosynthetic pathway
LuxY encodes for an antenna protein called yellow fluorescent protein
YFP lowers the energy state of the product from the luciferase reaction
Lux genes 2
The autoinducer concentration regulates the expression of lux genes
Bacteria become luminescent only at higher concentrations (quorum sensing)
No rapid regulation of light emission
Flashlight fish
Hunting close to the surface
Short pulses of light
Pigmented lids to cover the light organs
Other species can rotate the light organs to block the light
Applications of bioluminescence
Aequorin based intracellular calcium sensors
BRET sensors to proof protein interaction in the living cell
Reporter systems of gene activity
Sensor bacteria (heavy metals, explosives, water quality)
- advs, low background high sensitivity
- substrates cannot always be synthesised by the cells
