Nitric Oxide Synthase: Difference between revisions

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Michael Skovbo Windahl, Sara Toftegaard Petersen, Mathilde Thomsen, Mette Trauelsen, Eran Hodis, Jaime Prilusky, Karl Oberholser, Alexander Berchansky, Michal Harel, Ann Taylor

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 <applet load='2g6h' size='300' frame='true' align='right' caption='Tetrahydrobiopterin' />
-<scene name='Sandbox_5/Nos_oxygenase_bh4/11'>H4B</scene> is a cofactor. NOS contains two molecules of <scene name='Sandbox_5/Begge_h4b/1'>H4B</scene>, one in each monomer. The active center forms a kind of <scene name='Nitric_oxide_synthase/Substratebinding_distal_pocket/1'>tunnel</scene>, because of the dimeric structure. This gives H<sub>4</sub>B the opportunity to play a big role in the control of subunit interactions and active-center formation. H<sub>4</sub>B therefor is more of a structurel cofactor, in that it keeps the dimer stabilized by integration in to the hydrophobic parts of the dimer. Here it helps substrate interactions by lining the active-center channel and hydrogen bonding to the heme propionate amd to alfa7 which is two elements involved in L-Arg binding. Its structural importense is also reconned to play a role in dimer formation, and major conformational changes leading to the formation of the active site channelform<ref>PMID:9875848</ref>.
+<scene name='Sandbox_5/Nos_oxygenase_bh4/11'>H4B</scene> is a cofactor. NOS contains two molecules of <scene name='Sandbox_5/Begge_h4b/1'>H4B</scene>, one in each monomer. The active center forms a kind of <scene name='Nitric_oxide_synthase/Substratebinding_distal_pocket/2'>tunnel</scene>, because of the dimeric structure. This gives H<sub>4</sub>B the opportunity to play a big role in the control of subunit interactions and active-center formation. H<sub>4</sub>B therefor is more of a structurel cofactor, in that it keeps the dimer stabilized by integration in to the hydrophobic parts of the dimer. Here it helps substrate interactions by lining the active-center channel and hydrogen bonding to the heme propionate amd to alfa7 which is two elements involved in L-Arg binding. Its structural importense is also reconned to play a role in dimer formation, and major conformational changes leading to the formation of the active site channelform<ref>PMID:9875848</ref>.
 [[image:h4b hydrogenbindinger.png|thumb|left|Hydrogenbondings in H<sub>4</sub>B binding site]]
 The H<sub>4</sub>B is bound by hydrogen-bonds to several of the molekules surrounding it, including the substrate L-Arg. The substrate is H-bonded to the 4-keto group of pterin, and to one of the heme propionate groups, that has two carboxylate oxygens in use for H-bonds. These oxygens are further H-bonded to the 4-keto group of pterin, through water, and directly to N(3) and NH<sub>2</sub> on C (2)<ref>PMID:9875848</ref>. The big picture of all the H-bonds can be seen by clicking on the figure on the left. [[image:mette.png|thumb|right|model for NOS oxygen activation]]