Hi, my name is Gustavo Silva and I'm an Assistant Professor of Biology here Duke University.
And in this video we're going to talk about protein diversity, how the structure and function of protein
can control life has we know it.
We all know that our body is composed of trillions of trillions of tiny little cells
that has a ton of molecules inside of it. But have you ever thought about how each one of the
functions of our body can be controlled at the molecular level?
Have you ever thought that very important process like walking and talking or even
promoting respiration or digestion can be controlled by tiny little molecules?
So something very very interesting in biology is that all those functions can be controlled by protein.
Or many of the functions that we know and are important, can be controlled by proteins.
So when we think about walking you have specific motor proteins that can just slide over each other
and make your body move. In the process of respiration
you have a very unique protein called hemoglobin, inside our red blood cells, that binds oxygen from the air
and drives them to specific tissues in the process of making energy.
So to participate in each one of those processes
You already can imagine that you need thousands of different proteins to do each one of those functions.
So if it's a motor protein, a protein that allows you to make moves,
you need to have a certain shape and form so they can actually perform that function.
In terms of respiration you need a protein that is able to accommodate an oxygen molecule and drive
down to tissues. So each of those proteins, they have to have something very unique a certain shape
or what we call a 3d structure that allows them to perform each one of those functions.
So, I think it's easier now to understand that our body does a lot of different functions
and that they might need a lot of unique proteins. But
where did this proteins come from?
So some of you might be saying, yeah, it comes from our diet. So we're eating proteins all the time
we're always talking about this food or that food that is rich in protein.
But can you use the protein that you just ingested from your diet, can you use it the way that it is?
And the answer is actually no.
So if you think about a plant or if you think about an animal, that protein was not just a source of food.
It had a function in that organism. So what it's really important here to know is that our body would process
those proteins into small little pieces. So every time you eat something that is rich in proteins
your body is able to process and chop them into small building blocks
that then your cells are able to uptake to create the proteins that you need.
And what is really interesting is that in nature, all living organisms use the same building blocks
and that's what we call amino acids. So we have 20 different types of building blocks.
That is the same if you think about a plant or if you think about bacteria or if you think about us.
It's the same type of building blocks that are used to make and create those proteins
So every time we eat something that is rich in proteins, our body's gonna process into these small
building blocks so then we can uptake them and then assemble our own proteins.
So then the question is how do we know how to put a protein together? What's the right order?
So the answer is in your DNA. So your DNA has all the information that allows your cells to make
thousands and thousands of unique protiens. So when we think about our DNA,
this is our genetic material, it has a certain language because the DNA also has its own building blocks
which is called nucleotides. So we have four types of nucleotides that compose the DNA.
and the DNA have this recipe to promote and produce each one of those unique proteins.
But you cannot just take from DNA and make protein. So in this process, your cells are going to make
a copy of that DNA into molecule that is called RNA. So it's a different type of molecule
but it uses still the same building blocks or similar nucleotides to make RNA. But it's kind of like
making a copy of a page of that book, and then taking to your kitchen
so you can assemble all those ingredients together.
So that copy is called messenger RNA, and this process is called transcription.
So during transcription you're making a copy of that recipe for a given protein
and that's what cells are going to use to make the protein.
And to make that protein, there is a molecular complex inside of cells called Ribosomes.
and the Ribosomes are going to be able to read that RNA or that messenger RNA,
and then start putting those building blocks together.
And this process called translation. So the name comes from because you're using different alphabet now
that goes from nucleotides, and that's what you had in DNA and RNA, to now amino acids.
so different building blocks to make each one of those unique molecules.
So, the RNA is going to be a copy for one single protein they're going to have the recipe
and then the ribosome is this molecular machine that is going to be able
that is going to be able to assemble, each one of those amino acids in the right order.
So we've been talking about how the information can travel from the mRNA to then make a protein
but we still haven't talked about how proteins can achieve its final structure in its final function.
So something that is really important to know is that between those 20 different amino acids you have
four main groups. Between those four main groups
one of them is what we call hydrophilic, those are the ones that interact well with water,
and you have another one that are called hydrophobic. So those do not interact well with water.
Between those two boots the hydrophilic wants to be close to each other
and the hydrophobic wants to be close to each other.
The other two classes, those are based on electrical charges.
You have amino acids that can be positively charged amino acids that can be negatively charged.
And in this case, if you have positively charged amino acids, they don't like to be close to each other
so they usually repel each other.
At the same time, they are attracted to amino acids that have a negative charge.
So in this case of this protein that we assembled here
that you have, each one of those beads representing a unique amino acid.
We know that they're not just beads on a string, they are not just linear protein. They actually have a 3D structure
that allows them to perform a certain function. But how is this 3D structure achieved?
So now knowing that for example you have hydrophobic amino acids in this structure,
they want to be close together
so that protein will start to fold in on itself. But as they do this, you can bring other amino acids that don't want
to be close to each other, like those two red ones here with the red ones on top.
So then the proteins start folding in a different direction.
As you can see now it brings the yellow close to eachother, this can go
away from the other group of yellow
and eventually the protein will achieve its final 3D structure that allows them to perform unique functions.
So now we know that the human DNA encodes the information
to make about 20 to 25,000, different proteins.
So all of those have unique features as they have unique length, but also unique sequences.
And we know that information coming from DNA being converted into mRNA and then into protein
is what we call the central dogma of molecular biology. And all this information is encoded in your DNA
is what makes us who we are. But at the same time,
this information is what makes plants who they are, or even microbes because
all of them follow the same dynamics that you have your information or genetic material encoded in your DNA
that can be transformed into mRNA and be translated into proteins. And proteins are very important to
conduct, each one of those functions that we have, and it's only in this big cookbook of life.