From DNA to Protein, Introduction

                 Many of my previous posts have discussed work with individual proteins.  In the case of Diabetes mellitus, the importance of insulin was paramount.  In the Spanish Influenza series, I focused heavily on the protein hemaglutinin.  Thiaminase I took center stage in my mini-series on Australian vitamins while Taq polymerase was key to the polymerase chain reaction in An Extreme Solution.

                How do we know these things about individual proteins?  Well, they were isolated from the rest of cells and studied individually.  

                How do you go about isolating a one protein from the soup of proteins available within the cell?  Ah.  This is what my next few posts are going to focus on.  These steps are commonly referred to protein expression and purification.  What I plan to cover is the most straightforward way to isolate protein, but should not be considered the only way to do so or even to study individual proteins.  Scientists have all sorts of tricks in their bags!

                Protein expression and purification is broken into three steps (Figure 42.1):

Step One: Cloning/DNA preparation.  The necessary DNA is represented by the circle.

Step Two: Bacterial growth/expression.  The bacteria (gray boxes) with our protein of interest inside (red triangles) are shown.

Three: Protein Purification.  Eventually we just want our protein (red triangles) away from everything else.

                In Figure 42.1, I’ve given you a pictorial overview of where we are going.  It’s not supposed to make sense right now.  However, I hope at the end of this series, it will make a lot of sense!

                Several layers of understanding exist for explaining the above steps.  Obviously I understand down to the extreme nitty-gritty, which is probably way more than any of you would like to know.  It is also quite easy to get lost in the details and confuse everyone with what I’m discussing.  For these reasons, I’m planning on breaking each post into two parts: the first part will fall under the EASY category and discuss very plainly what is going on; the second part will be more INTERMEDIATE/DIFFICULT and will discuss the same ideas as the first part, but in more detail and with more scientific considerations in mind.  Whether you read one or both parts is completely up to you!  I also won’t dive all the way down to the all minutiae so ask any questions you wish!