View source for 1dmm

[[Image:1dmm.gif|left|200px]]<br /><applet load="1dmm" size="450" color="white" frame="true" align="right" spinBox="true" 
caption="1dmm, resolution 1.9&Aring;" />
'''CRYSTAL STRUCTURES OF MUTANT ENZYMES Y57F OF KETOSTEROID ISOMERASE FROM PSEUDOMONAS PUTIDA BIOTYPE B'''<br />

==Overview==
Delta(5)-3-Ketosteroid isomerase from Pseudomonas putida biotype B is one, of the most proficient enzymes catalyzing an allylic isomerization, reaction at rates comparable to the diffusion limit. The hydrogen-bond, network (Asp99... Wat504...Tyr14...Tyr55...Tyr30) which links the two, catalytic residues, Tyr14 and Asp99, to Tyr30, Tyr55, and a water molecule, in the highly apolar active site has been characterized in an effort to, identify its roles in function and stability. The DeltaG(U)(H2O), determined from equilibrium unfolding experiments reveals that the, elimination of the hydroxyl group of Tyr14 or Tyr55 or the replacement of, Asp99 with leucine results in a loss of conformational stability of, 3.5-4.4 kcal/mol, suggesting that the hydrogen bonds of Tyr14, Tyr55, and, Asp99 contribute significantly to stability. While decreasing the, stability by about 6.5-7.9 kcal/mol, the Y55F/D99L or Y30F/D99L double, mutation also reduced activity significantly, exhibiting a synergistic, effect on k(cat) relative to the respective single mutations. These, results indicate that the hydrogen-bond network is important for both, stability and function. Additionally, they suggest that Tyr14 cannot, function efficiently alone without additional support from the hydrogen, bonds of Tyr55 and Asp99. The crystal structure of Y55F as determined at, 1.9 A resolution shows that Tyr14 OH undergoes an alteration in, orientation to form a new hydrogen bond with Tyr30. This observation, supports the role of Tyr55 OH in positioning Tyr14 properly to optimize, the hydrogen bond between Tyr14 and C3-O of the steroid substrate. No, significant structural changes were observed in the crystal structures of, Y30F and Y30F/Y55F, which allowed us to estimate approximately the, interaction energies mediated by the hydrogen bonds Tyr30...Tyr55 and, Tyr14...Tyr55. Taken together, our results demonstrate that the, hydrogen-bond network provides the structural support that is needed for, the enzyme to maintain the active-site geometry optimized for both, function and stability.

==About this Structure==
1DMM is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Pseudomonas_putida Pseudomonas putida]. Active as [http://en.wikipedia.org/wiki/Steroid_Delta-isomerase Steroid Delta-isomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.3.3.1 5.3.3.1] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1DMM OCA]. 

==Reference==
Contribution of the hydrogen-bond network involving a tyrosine triad in the active site to the structure and function of a highly proficient ketosteroid isomerase from Pseudomonas putida biotype B., Kim DH, Jang DS, Nam GH, Choi G, Kim JS, Ha NC, Kim MS, Oh BH, Choi KY, Biochemistry. 2000 Apr 25;39(16):4581-9. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=10769113 10769113]
[[Category: Pseudomonas putida]]
[[Category: Single protein]]
[[Category: Steroid Delta-isomerase]]
[[Category: Choi, K.Y.]]
[[Category: Jang, D.S.]]
[[Category: Kim, D.H.]]
[[Category: Nam, G.H.]]
[[Category: Oh, B.H.]]
[[Category: closed barrel]]
[[Category: coneshell]]
[[Category: curved b-sheet]]

''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Tue Nov 20 13:24:57 2007''