July 17, 2019 Wednesday
Bedtime Story
G Protein-Coupled Receptors
The exact molecular functioning and
workings of these complex molecules have only come to be known in the last 50
years with the Nobel Prizes in this field coming about since 1970s.
For instance, it was only in 1971 that
Nobel Prize in Physiology or Medicine was awarded for discovering key role of
adenylate cyclase which produces the second messenger cyclic AMP.
It was in 1994 that Nobel Prize in
Physiology or Medicine was awarded for the discovery of “G-proteins and the
role of these proteins in signal transduction in cells”.
Furthermore, it was only in 2000 that Nobel
Prize in physiology or Medicine was awarded for research on neurotransmitters
such as dopamine that act via G-protein coupled receptors.
What is most surprising is that it was as
recent as in 2012 that the Nobel Prize in Chemistry was awarded two American
biochemists for their work on the functioning of G-protein coupled receptors.
Two of the top ten selling drugs worldwide
(Fluticasone/Salmetrol combination and Aripriprazole) have their mechanism of
action operating through these G-protein coupled receptors.
Not surprisingly both my mother and I have
taken the former drug combination (Fluticasone/Salmetrol) through metered-dose
inhalers that delivers a specific amount of drug into the lungs through a short
bust of aerosolized drug pumped out by the patient himself.
I can guarantee you that my mother is alive
today (for good or for worse that is debatable and perhaps meaningless) because
of this wonder drug combination and without it no prayers would have worked.
G-protein coupled receptors play significant
role in wide range of physiological functions of organisms:
(a) Vision: the light sensitive pigments
opsins that are found in the photoreceptors of retina and which posses that magical
ability to convert a photon into an electrochemical signal belongs to transporter-opsin-G
protein-coupled receptor super family.
They are believed to have evolved some 650
million years ago from primitive G-protein couple receptor.
(b) Taste or gustatory function: some taste
receptor cells contain a G-protein known as gustducin that was discovered just
27 years ago in 1992.
Of the five basic tastes – sweetness,
sourness, saltiness, bitterness and umami (savory taste of broths or cooked
meat much to the chagrin of vegans and vegetarian Hindus that was first scientifically
identified by a Japanese Chemist Kikunae Ikeda in 1908) – the G-protein coupled
receptors are responsible for three of them - sweet, bitter and umami.
(c) Smell or olfaction – both odor and
pheromones are capable of stimulating olfactory receptors located on the cilia
of olfactory receptor neuron.
These olfactory receptors are nothing but a
specialized G protein-coupled receptor and about one-thousand different genes
code for these proteins.
This is the largest gene family and
understandably so.
Stay tuned to the voice of an
average story storytelling chimpanzee or login at http://panarrans.blogspot.com
Good night Mon Ami and my fellow cousin ape.
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Another great educator and a teacher that I am aware of is
Professor Subhashish Chattopadhyay in Bangalore, India.
While I narrate stories, Professor Subhashish an electronic
engineer and a former professor at BARC, does and teaches real mathematics and
physics.
He started the participation of Indian students at the
International Physics Olympiad.
Do visit him here:
All his books can be downloaded for free through this link:
For edutainment and English education of your children, I
recommend this large collection of Halloween Songs for Kids:
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