View source for 1uxh

[[Image:1uxh.gif|left|200px]]<br /><applet load="1uxh" size="350" color="white" frame="true" align="right" spinBox="true" 
caption="1uxh, resolution 2.10&Aring;" />
'''LARGE IMPROVEMENT IN THE THERMAL STABILITY OF A TETRAMERIC MALATE DEHYDROGENASE BY SINGLE POINT MUTATIONS AT THE DIMER-DIMER INTERFACE'''<br />

==Overview==
The stability of tetrameric malate dehydrogenase from the green phototrophic bacterium Chloroflexus aurantiacus (CaMDH) is at least in part determined by electrostatic interactions at the dimer-dimer interface. Since previous studies had indicated that the thermal stability of CaMDH becomes lower with increasing pH, attempts were made to increase the stability by removal of (excess) negative charge at the dimer-dimer interface. Mutation of Glu165 to Gln or Lys yielded a dramatic increase in thermal stability at pH 7.5 (+23.6 -- + 23.9 degrees C increase in apparent t(m)) and a more moderate increase at pH 4.4 (+4.6 -- + 5.4 degrees C). The drastically increased stability at neutral pH was achieved without forfeiture of catalytic performance at low temperatures. The crystal structures of the two mutants showed only minor structural changes close to the mutated residues, and indicated that the observed stability effects are solely due to subtle changes in the complex network of electrostatic interactions in the dimer-dimer interface. Both mutations reduced the concentration dependency of thermal stability, suggesting that the oligomeric structure had been reinforced. Interestingly, the two mutations had similar effects on stability, despite the charge difference between the introduced side-chains. Together with the loss of concentration dependency, this may indicate that both E165Q and E165K stabilize CaMDH to such an extent that disruption of the inter-dimer electrostatic network around residue 165 no longer limits kinetic thermal stability.

==About this Structure==
1UXH is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Chloroflexus_aurantiacus Chloroflexus aurantiacus] with <scene name='pdbligand=NAD:'>NAD</scene> and <scene name='pdbligand=FMR:'>FMR</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Malate_dehydrogenase Malate dehydrogenase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.1.1.37 1.1.1.37] Known structural/functional Site: <scene name='pdbsite=AC1:Fmr+Binding+Site+For+Chain+B'>AC1</scene>. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1UXH OCA]. 

==Reference==
Large improvement in the thermal stability of a tetrameric malate dehydrogenase by single point mutations at the dimer-dimer interface., Bjork A, Dalhus B, Mantzilas D, Sirevag R, Eijsink VG, J Mol Biol. 2004 Aug 27;341(5):1215-26. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=15321717 15321717]
[[Category: Chloroflexus aurantiacus]]
[[Category: Malate dehydrogenase]]
[[Category: Single protein]]
[[Category: Bjork, A.]]
[[Category: Dalhus, B.]]
[[Category: Eijsink, V G.H.]]
[[Category: Mantzilas, D.]]
[[Category: Sirevag, R.]]
[[Category: FMR]]
[[Category: NAD]]
[[Category: malate dehydrogenase]]
[[Category: oxidoreductase]]
[[Category: tricarboxylic acid cycle]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 15:29:23 2008''