Proteins and Bioluminescence -13

Comprehensive practice questions covering protein biochemistry, bioluminescent mechanisms (specifically Aequorea victoria and bacterial systems), genetic regulation via lux genes, and marine biological applications.

What is bioluminescence and what characterizes its heat emission?

Bioluminescence is biologically produced light, also known as "cold light" because it does not emit any heat.

What are the two primary components involved in the generic enzymatic reaction for bioluminescence?

The reaction involves a substrate called a Luciferin and an enzyme called a Luciferase, typically consuming $O_2$ at some stage in an oxidation reaction.

According to the lecture, what are two examples of marine organisms using bioluminescence for hunting?

Malacosteus niger and Anomalops sp.

How do fish and squid use bioluminescence for camouflage?

They use countershading via light-bearing organs on their underside to blend into the lighter waters above them, making them harder for predators beneath to see.

What chemical structure found in dinoflagellates is similar to those in haemoglobin and chlorophyll?

The circular tetrapyrrole structure, which in chlorophyll has magnesium at the center and forms systems of carbon rings and double bonds (conjugated systems).

According to Shimomura et al. (1962), what is Aequorin composed of?

An enzyme-substrate complex of apoaequorin (the enzyme) and coelenterazine (the substrate).

What cofactor is required to induce a conformational change in Aequorin and release photons?

$$Ca^{2+}$$

What is the specific wavelength of the light released by Aequorin?

$$466\,nm$$

What tripeptide sequence forms the Green Fluorescent Protein (GFP)?

Ser-Tyr-Gly

What are the two essential requirements for Bioluminescence Resonance Energy Transfer (BRET) or FRET to occur?

Spectral overlap and close proximity ($1-10\,nm$ or $10-100\,\text{\AA}$).

In Aequorea victoria, how do GFP and Aequorin interact to produce green light?

The blue light produced by Aequorin excites the GFP, which then absorbs that light and remits it as green light.

Which genes in the bacterial right lux operon code for the luciferase subunits?

luxA and luxB

What are the functions of the luxCDE genes in the bacterial bioluminescent system?

They code for the fatty acid reductase polypeptides.

What is the function of the luxI gene?

It is responsible for synthesizing the autoinducer.

What does LuxY encode, and what is its effect on the bioluminescence reaction?

It encodes an antenna protein called yellow fluorescent protein (YFP), which lowers the energy state of the product from the luciferase reaction.

How is bacterial bioluminescence regulated in terms of symbiosis and the environment?

It is regulated by the concentration of the autoinducer, which triggers quorum sensing to express lux genes only at higher concentrations.

How does the Flashlight fish (Photoblepharon sp.) regulate its light emission for hunting and protection?

It uses pigmented lids to cover its light organs and swims in an irregular zig-zag pattern to confuse predators.

What are some modern applications of bioluminescence mentioned in the notes?

Aequorin-based intracellular calcium sensors, BRET sensors for protein interaction, reporter systems for gene activity, and sensor bacteria for heavy metals or explosives.

What are the advantages and drawbacks of using bioluminescent systems compared to fluorescent dyes?

Advantages include low background and high sensitivity; drawbacks include the fact that substrates cannot always be synthesized by the cells.