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Functional Analysis of KV1.2 and Paddle Chimera Kv Channels in Planar Lipid Bilayers is a scientific article written by Xiao Tao and Roderick MacKinnon and devoted to the role of voltage-dependant K+ channels during the process of shaping electric signals in excitable and nonexcitable cells.
The peculiar feature of these channels is that they can be open and close depending on any voltage changes, which may happen within the cell membrane. The authors of this article analyze two different atomic structures: the first one is of a mammalian Kv channel (Kv 1.2) and the second one is of a mutant Kv channel (where Kv 1.2 is transferred into Kv 2.1), also called ‘paddle chimera’. One of the major purposes of this research is to find out the differences and similarities of Kv 1.2 and Kv 2.1 channels’ properties and functions.
It is necessary to admit that there are lots of different studies, which attempt to analyze this voltage-sensing mechanism. This very issue is considered to be one of the most frequent subjects of study in biology, medicine, and electrophysiology.
Electrophysiology aims at determining the functions of the paddle chimera channel and Kv 1.2 channel, defining their similarities and differences, and describing the properties, which are inherent to both channels. With regard to a cell biological process, it is obligatory to mention that scientists want to analyze electrical signaling and clear up how exactly a protein may sense the voltage of membrane.
Lots of scientists spend much time to answer this question, however, the results were quite unclear; this is why the authors of this work make an attempt to conduct the researches in their laboratories and give a clear answer and present the analysis of Kv 1.2 and Kv 2.1 (paddle chimera) channels in the frames of planar lipid bilayers.
They determine the structures of both channels in order to get an opportunity to find out their functional properties. The authors also acknowledge the participation of the Howard Hughes Medical Institute in their investigation. This point proves that the ideas, presented in this article, are also important to the sphere of medicine.
The results of this research play a significant role in biology, electrophysiology, and medicine, so that it is possible to say that this investigation means a lot for people in the world and for their safe and healthy future. The major point is that is the investigations do not harm to any human being, bring certain results, and make contribution into the science, such investigations are really significant and cannot be neglected.
Methods and Results
The authors choose three different methods to analyze the functions and changes, which happen within these two channels, and call them protein preparation, channel reconstitution, and electrophysiology. The method of channel reconstitution will be described below and its results turn out to be quite impressive. First, voltage-dependant activation takes place.
The researchers reconstitute Kv 1.2 and paddle chimera channels into lipid vesicles (POPE into POPG), and then, mix them with planar bilayers with the same lipid composition. The figure 1 describes the paddle chimera channels, and the figure 2 introduces the channel activation process itself.
These figures and their legends, described below them, give a clear picture of what influences the changes, and how exactly it happens. The experiments help to make a conclusion that both channels are certainly voltage-dependent. Further, the process of inactivation takes place, which is characterized by spontaneous closure because of prolonged depolarization. The figure 3 illustrates the changes, which are caused by channels’ inactivation.
The results also show that, because of Pichia yeast, Kv 1.2 and Kv 2.1 channels may easily produce voltage-dependant functions with the same lipid composition: “voltage dependent activation upon depolarization followed by slow inactivation, presumably C-type.” (Tao and MacKinnon 2008, p. 30)
Because of the process of inactivation, certain differences between structural and electrophysiological data appear. It is necessary to point out that the crystal structure of paddle chimera does not react to an inactivated conformation. Kv 1.2 and Kv 2.1 are different with their “amino acid sequence of the voltage sensor.” (Tao and MacKinnon 2008, p. 31) This very difference of the channels’ components and their sensitivity causes certain differences between their functions.
Discussion and Conclusions
The results of the investigation, described in the work by Xiao Tao and Roderick MacKinnon turn out to be rather education and useful for different studies. Functional Analysis of KV1.2 and Paddle Chimera Kv Channels in Planar Lipid Bilayers is the article about the relations of Kv 1.2 channel and Kv 2.1 channel (also called ‘paddle chimera’), their functions, and properties.
It is proved that channels’ properties considerably influence their functions and reactions to different changes. “The voltage sensor paddle has the interesting structural property of being titled away from other helices in the channel.” (Tao and MacKinnon, 2008, p.31)
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Due to this property, voltage sensor paddle’s structure entails the open conformation. The investigators also prove that Pichia yeast create perfectly functioning Kv 1.2 channels (with the features of Shaker K+ channel). The paddle chimera channel demonstrates the same functions and reactions, however, certain differences are still noticed.
After the results of the investigation are analyzed, it is possible to say that there should be something different between cellular and bilayer systems. These differences may be found in the membrane or the cytoplasm and may be certainly influences the functions of any channel.
This is why it is crucially important to analyze these differences in future: clear up what exactly may cause these differences and find out how these differences can influence Kv 1.2 and paddle chimera channels. Such investigations may be carried out by the representatives of biological, medical, or electrophysiological spheres.
Due to the work of electrophysiological researchers, it is possible to concentrate on the properties of paddle channel and Kv 1.2 channel. Biological and medical approaches will help to analyze the structure of the membrane and the cytoplasm. This is why impact of Pichia yeast remains considerable and should be taken into consideration further.
In conclusion, we should admit that the analysis of Kv 1.2 and paddle chimera channels, described by the authors of this article, is rather clear and significant. Images and statistics offered help to get a clear understanding of how the described processes happen and what reactions play more considerable role.
Planar lipid bilayers, where the changes take place, have the same composition; because of the same composition, it is easier to find out the differences between the reactions of paddle chimera and Kv 1.2 channels. This is why we may conclude that the results of this investigation are clear and strong, and may be used for further researchers in the same spheres.
Tao, Xiao and MacKinnon, Roderick.“Functional Analysis of KV1.2 and Paddle Chimera Kv Channels in Planar Lipid Bilayers.” Journal of Molecular Biology 382 (2008): 24-33.