To the average person, the term ‘protein expression’ is likely rather foreign. It is not something that is come across regularly in day to day life, so most people probably do not know what protein expression refers to, or why it is important. In fact, this term can actually refer to two specific things, a fact which only goes to further the potential confusion.
What Is Protein Expression?
Protein expression refers to the way in which proteins are synthesized, modified and regulated in living organisms.
Protein expression can refer to the object of study in protein research, or it can reference the actual lab techniques which are being used to create proteins. The meaning of this term will depend on the context in which it is being used.
In the case of this article, we will be covering a little bit about the second meaning – that is, protein expression that covers lab techniques.
The Basics To Protein Expression
The use of proteins depends on the actual needs of each individual cell. DNA is responsible for storing protein blueprints, and messenger RNA is created in order to translate DNA messages into an actual protein. The word ‘transcription’ is often used in the world of protein expression, and it refers to the information that is moving from DNA to mRNA. Translation, on the other hand, is the actual synthesis of a protein that occurs thanks to the mRNA in question.
In some cases, the processes of transcription and translation can take place at the same time, while in other cases they occur in order, with transcription followed by a translation. Transcription and translation are able to take place at the same time prokaryotes, while they operate sequentially in eukaryotes.
Transcription and Translation Process
Each of these two processes included three steps, which are initiation, elongation, and termination. The transcription part of the process starts when the DNA is unwound, allowing RNA polymerase binding. There are differences in transcription between eukaryotes and prokaryotes, specifically the fact that no modification of mRNA is needed in prokaryotes. However, when it comes to translation, the process is similar for both prokaryotes and eukaryotes, despite the presence of some differences.
Once transcription and translation are complete, there is a process of post-translational modification that can occur to further complete the structure that has been created. These PTMs can serve to make additions or alterations to the chemical structure, they can designate locations, or regulate activity within a cell. For example, disulfide bridge formation or reduction would be one instance of a post-translational modification.
Protein Expression Methods
It is necessary for a variety of research fields to produce functional proteins that can then be studied. Since DNA is relatively simple to construct through synthetic or in vitro methods, it can be used as a template for protein expression. When a protein is created from a DNA template, the result is known as a recombinant protein.
Protein expression can be done either in vivo or in vitro. Although in vivo systems typically will produce a functional protein, they also don’t produce a large number of proteins and the process is rather expensive. In vitro methods offer advantages over in vivo, specifically the speed of the process and the simplicity of expressing many different proteins simultaneously.
As a third option, chemical protein synthesis can also be used, and it is able to produce highly pure protein, although only with small proteins and peptides. Longer polypeptides would be too expensive to produce with a chemical process.
Protein expression is an incredibly deep and complex topic, and the content above simply scratches the surface of this field of science. Understanding the basics of translation and transcription, along with methods such as in vivo and in vitro are the first step on a long journey toward educating yourself in the world of protein expression.