In this video, we're going to talk a little bit more about one of the 5 types of ATPases, the ABC transporters. The main takeaway of this video is that ABC transporters can provide multidrug resistance. The ABC part of ABC Transporters stands for ATP binding cassette, ABC. The ATP binding cassette transporters or ABC transporters are integral membrane proteins of secondary structures and proteins. ABC transporters are a type of ATPase, they are a form of primary active transport. It's no surprise that these transporters pump substances across the membrane against their concentration gradient, from areas of low concentration to areas of high concentration.
Another defining feature of these ABC transporters are the structural elements that they contain. All ABC transporters share two common structural elements. The first is that they all contain two transmembrane domains (TMDs) which are transmembrane, so they span the membrane. This helps create a pore through the membrane that allows them to transport molecules across the membrane. The second common structural element that all ABC transporters have is that they all have two cytosolic Nucleotide Binding Domains (NBDs). These nucleotide binding domains will bind and hydrolyze ATP, which is a nucleotide known for its energy-transfer capabilities. Within these nucleotide binding domains, is found the ATP binding cassette, this specific structural motif.
If we take a look at our image below, we're showing you an ABC transporter embedded within this plasma membrane. Notice that, spanning the membrane there are these two transmembrane domains highlighted here in pink, and then on the cytosolic side of the cell, we have these two nucleotide binding domains (NBDs) here. The nucleotide binding domains can bind and hydrolyze ATP as we see here. This exactly matches the description of the two TMDs and two NBDs.
It's also important to note that some ABC Transporters are called multidrug resistance (MDR) transporters, and they are particularly responsible for resistance to multiple drugs. In bacteria, MDR transporters confer antibiotic resistance. In humans, there's a protein called P-glycoprotein or PGP, which is an MDR transporter that removes anticancer drugs from tumor cells. MDRs are of great importance to humans because they can confer antibiotic resistance in bacteria, creating a health problem for humans. A lot of research goes into MDR transporters to see how we can work around those providing antibiotic resistance in bacteria, and also in humans, as P-glycoprotein can remove anticancer drugs in tumor cells, which is problematic and a highly researched area.
You'll notice here we have a tiny stethoscope over here on the left, a symbol that we're going to use moving forward in our course to represent something that you might want to pay close attention to, especially if you're going on into medical school or some kind of other medical profession like pharmacy. Wherever we have this symbol, this is a place where you might want to hone in and keep this idea in mind in case you encounter this idea again. If we take a look at our image below, notice that we're showing you these red lines here, that are taking toxins and drugs and pumping them to the outside of the cell. ABC transporters or MDR transporters can take toxins or drugs that are embedded within the plasma membrane and remove them, pump them to the outside of the cell, and they can also take drugs that are in the cytoplasm and toxins that are in the cytoplasm and remove them and pump them to the outside of the cell against their concentration gradient while utilizing and hydrolyzing ATP.
This concludes our lesson on ABC Transporters, and as we move forward in our course we'll be able to get some practice applying these concepts. I'll see you guys in our next video.
