2b7s: Difference between revisions

[[Image:2b7s.gif|left|200px]]<br /><applet load="2b7s" size="350" color="white" frame="true" align="right" spinBox="true"  

The mechanism for fumarate reduction by the soluble fumarate reductase from Shewanella frigidimarina involves hydride transfer from FAD and proton transfer from the active-site acid, Arg-402. It has been proposed that Arg-402 forms part of a proton transfer pathway that also involves Glu-378 and Arg-381 but, unusually, does not involve any bound water molecules. To gain further insight into the importance of this proton pathway we have perturbed it by substituting Arg-381 by lysine and methionine and Glu-378 by aspartate. Although all the mutant enzymes retain measurable activities, there are orders-of-magnitude decreases in their k(cat) values compared with the wild-type enzyme. Solvent kinetic isotope effects show that proton transfer is rate-limiting in the wild-type and mutant enzymes. Proton inventories indicate that the proton pathway involves multiple exchangeable groups. Fast scan protein-film voltammetric studies on wild-type and R381K enzymes show that the proton transfer pathway delivers one proton per catalytic cycle and is not required for transporting the other proton, which transfers as a hydride from the reduced, protonated FAD. The crystal structures of E378D and R381M mutant enzymes have been determined to 1.7 and 2.1 A resolution, respectively. They allow an examination of the structural changes that disturb proton transport. Taken together, the results indicate that Arg-381, Glu-378, and Arg-402 form a proton pathway that is completely conserved throughout the fumarate reductase/succinate dehydrogenase family of enzymes.

2B7S is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Shewanella_frigidimarina Shewanella frigidimarina] with <scene name='pdbligand=NA:'>NA</scene>, <scene name='pdbligand=HEM:'>HEM</scene>, <scene name='pdbligand=FAD:'>FAD</scene> and <scene name='pdbligand=FUM:'>FUM</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Succinate_dehydrogenase Succinate dehydrogenase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.3.99.1 1.3.99.1] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2B7S OCA].  

[[Category: Chapman, S K.]]

[[Category: Miles, C S.]]

[[Category: Mowat, C G.]]

[[Category: Pankhurst, K L.]]

[[Category: Reid, G A.]]

[[Category: Rothery, E L.]]

[[Category: Walkinshaw, M D.]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:35:02 2008''