In today's lecture, we're going to be discussing the cellular mechanisms for
degrading intracellular proteins and the biological importance of this process.
Thus far in the course,
you've been concerned with systems for expression of genetic information.
The central dogma of modern biology is shown in the next slide.
This slide emphasizes that cell proteins are being
made off messenger RNA molecules encoded in DNA.
And the general assumption until recently was once proteins are made,
they are stable structures that basically live happily ever after.
Today we'd like to disabuse you of
this comfortable idea and replace it with another view of the cell.
This revised view emphasizes that proteins,
once synthesized, are short lived structure.
Their lives are nasty, brutish and short.
And this rapid destruction of cell proteins,
although seemingly highly wasteful,
is absolutely essential for viability.
As this slide's title implies,
we believe that protein breakdown is absolutely essential for viability.
In fact, this image is the official T-shirt on
my laboratory and it is sort of our philosophy of the research we do.
Specifically, what is shown here are
these complex molecular machines that are
responsible for the continual degradation of protein.
The large 26S proteasome shown on the left,
the core 20S proteasome particle inside which proteins are degraded on the bottom,
the form found in eukaryotic cells.
And on the top, the simpler symmetric proteasomes that are found in prokaryote.
Prokaryotes and mitochondria also have
other energy dependent proteolytic machines such as
the HslVU Complex which is a cousin of the proteasome,
a simpler earlier precursor.
But today we're going to focus on the process in the eukaryotic cells.
I would like to ask the very fundamental question.
First of all, of why cells degrade so rapidly many proteins?
It turns out that the most rapidly hydrolized proteins are among the most important,
the sexiest proteins in contemporary biology.
This slide shows a list of many of the most important proteins in the regulation of