Sandbox 212: Difference between revisions
Ndeye Coumba (talk | contribs) No edit summary |
Ndeye Coumba (talk | contribs) |
||
| Line 33: | Line 33: | ||
The core of the 2 domains is a 6-stranded mixed β-sheet (β10-β13, β15, β16 in the C domain), with 3 α-helices covering one of its faces (α6, α7, α12 in the N domain). The other face of the β-sheet in the N domain is covered by additional helices, whereas the other face of the β-sheet in the C domain is covered by the N domain. | The core of the 2 domains is a 6-stranded mixed β-sheet (β10-β13, β15, β16 in the C domain), with 3 α-helices covering one of its faces (α6, α7, α12 in the N domain). The other face of the β-sheet in the N domain is covered by additional helices, whereas the other face of the β-sheet in the C domain is covered by the N domain. | ||
* '''active site''' | * '''active site''' | ||
The <scene name='Sandbox_212/Active_site/1'>active site</scene> of CrAT is located at the interface between the N and C domains. Biochemical and mutagenesis studies have permitted to identify a histidine residue as the catalytic base of carnitine acyltransferases. | The <scene name='Sandbox_212/Active_site/1'>active site</scene> of CrAT is located at the interface between the N and C domains. Biochemical and mutagenesis studies have permitted to identify a histidine residue as the catalytic base of carnitine acyltransferases. It can be reached from two openings of the tunnel on the surface of the structure. One of these openings is used for binding carnitine, while the other is used for binding CoA. Hnce, the two substrates of the enzyme bind at opposite sides of the <scene name='Sandbox_212/Histidine343/1'> catalytic residue</scene>. | ||
* '''carnitine binding site''' | * '''carnitine binding site''' | ||
The carnitine substrate has to be positioned in a way that the proton of its hydroxyl group can interact with the nitrogen N3 of the catalytic residue histidine 343. Carnitine binding in the right position is made possible by electrostatic interactions and the formation of hydrogen bondings between the '''carboxylate group''' of carnitine and residues near the active site. The residues that form the carnitine binding site can be found in the C domain and in the N domain. | The carnitine substrate has to be positioned in a way that the proton of its hydroxyl group can interact with the nitrogen N3 of the catalytic residue histidine 343. Carnitine binding in the right position is made possible by electrostatic interactions and the formation of hydrogen bondings between the '''carboxylate group''' of carnitine and residues near the active site. The residues that form the carnitine binding site can be found in the C domain and in the N domain. | ||
| Line 40: | Line 40: | ||
There are only slight conformational changes in the enzyme upon carnitine binding.“The only significant conformational difference in the active site between the free enzyme and the carnitine complex is in the side chain of <font color='#90E050'>'''serine454'''</font>, which adopts a different rotamer to have better hydrogen-bonding interactions with the carboxylate of carnitine.” <ref name="structure" /></StructureSection> | There are only slight conformational changes in the enzyme upon carnitine binding.“The only significant conformational difference in the active site between the free enzyme and the carnitine complex is in the side chain of <font color='#90E050'>'''serine454'''</font>, which adopts a different rotamer to have better hydrogen-bonding interactions with the carboxylate of carnitine.” <ref name="structure" /></StructureSection> | ||
==Catalytic Mechanism of Carnitine Acyltransferases== | ==Catalytic Mechanism of Carnitine Acyltransferases== | ||
[[Image:Machanism fatty acid transfer.jpg|thumb|700px|left]] | [[Image:Machanism fatty acid transfer.jpg|thumb|700px|left]] | ||