| The TRP (Transient receptor potential) ion channels are a large family of ion channels which located on the cell membrane. Based on their sequence homology, mammalian TRP ion channels can be divided into six subfamilies:TRPC, TRPM, TRPV, TRPA, TRPML, TRPP. TRP ion channels which are used as cell receptors can be activated and controlled by a variety of mechanisms. TRPA1is a member of transient receptor potential protein (TRP) family. It is selectively expressed in hair and skin cells and in a subpopulation of neurons in the trigeminal, nodose ganglia and dorsal root. As well as other members of TRP, TRPA1plays an important role in sensory physiological functions in animals such as cold sensation, thermosensory, mechanical stimulation and pain perception. Through a specialized structure called pit organ, snakes can detect slight temperature change, as small as0.003℃. With this sensitive system, snakes can be more efficiently when they prey. In addition, Some studies show that Infrared sensation may play a important role in predator avoidance and thermoregulatory.Recently, a work by Gracheva et al. revealed the mechanisms of Infrared vision. A temperature-sensitive calcium ion channel, TRPA1was found to be responsible for Infrared vision. Infrared detection mechanism of snakes is different from visual transmission mechanism. The thermal threshold of TRPA1in three snakes (Boidae (boas), Pythonidae(pythons) and Crotalinae(pit vipers) were measured and theirs threshold Consisted with their infrared sensitivity. TRPA1occurred molecular convergence in the evolution of these three snakes. That evolutionary way may help snakes to adapt to different environment for the survival. As has been found, vampire bat(Desmodus rotundus) had the capability of Infrared vision, but TRPV1mediated the function of the infrared detection in the vampire bat. It’s not clear why this change occurred in mammals and reptiles. In addition, recent cellular experiments have demonstrated that snake TRPA1channels are heat-responsive, from the pit organ-containing snakes to non-pit snakes. Therefore, the role of pit-organ in the infrared detection process is still worth studying.At present study, the TRPA1cDNA from agkistrodon acutus (Deinagkistrodon acutus) was amplificatied and sequenced, then its amino acid sequence was predictecd. The cloned fragment and a variety of other species were used to compared with each other and a phylogenetic tree was established. After their work, the results and conclusions are as follows:1. A3287bp fragment of the TRPA1from agkistrodon acutus(Deinagkistrodon acutus) was amplificatied and sequenced, encoded1081amino acids. Multiple sequence alignment found that the TRPA1of agkistrodon acutus and Western Diamondback Rattlesnake was similarity up to92%, indicating that the infrared detection mechanism of the agkistrodon acutus may be the same as the Western Diamondback Rattlesnake.2. Compared with the TRPA1of western diamondback rattlesnake (Crotalus atrox), agkistrodon acutus TRPA1fragment missed90bp nucleotides in the coding region. These90bp fragment corresponded to30amino acid residues, the deletion of the fragment may result in a change of the TRPA1transmembrane domains. Its functions may be changed by this. Removed the fragment of the TRPA1of Western Diamondback Rattlesnake and compared to the original protein conformation,it was found that the deletion of the fragment leaded to a conformational change. It may prompts that the fragment was necessary to the function of TRPA1.3. The secondary structure and tertiary structure were speculated by some bioinformatics softwares. Folding areas and transmembrane domains were predicted. Agkistrodon acutus TRPA1has five transmembrane domains and15ankyrin repeat domains.4. Several species of the TRPA1amino acid sequence were selected, homology comparison found that the TRPA1has highly conserved region. A phylogenetic tree was built. The TRPA1has undergone a drastic change in evolution in reptiles and mammals. |
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