5clg

<table><tr><td colspan='2'>[[5clg]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Acetobacter_aceti_1023 Acetobacter aceti 1023]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5CLG OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=5CLG FirstGlance]. <br>

</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=CIT:CITRIC+ACID'>CIT</scene></td></tr>

<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[2fw6|2fw6]], [[5clf|5clf]], [[5clh|5clh]], [[5cli|5cli]], [[5clj|5clj]]</td></tr>

<tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">purE, AZ09_02690 ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=1457393 Acetobacter aceti 1023])</td></tr>

<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/5-(carboxyamino)imidazole_ribonucleotide_mutase 5-(carboxyamino)imidazole ribonucleotide mutase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.4.99.18 5.4.99.18] </span></td></tr>

<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=5clg FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5clg OCA], [http://pdbe.org/5clg PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=5clg RCSB], [http://www.ebi.ac.uk/pdbsum/5clg PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=5clg ProSAT]</span></td></tr>

== Function ==

[[http://www.uniprot.org/uniprot/A0A063X4U8_ACEAC A0A063X4U8_ACEAC]] Catalyzes the conversion of N5-carboxyaminoimidazole ribonucleotide (N5-CAIR) to 4-carboxy-5-aminoimidazole ribonucleotide (CAIR).[HAMAP-Rule:MF_01929]

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== Publication Abstract from PubMed ==

N5-carboxyaminoimidazole ribonucleotide (N5-CAIR) mutase (PurE) catalyzes the reversible interconversion of acid-labile compounds N5-CAIR and 4-carboxy-5-aminoimidazole ribonucleotide (CAIR). We have examined PurE from the acidophilic bacterium Acetobacter aceti (AaPurE), focusing on its adaptation to acid pH and the roles of conserved residues His59 and His89. Both AaPurE and Escherichia coli PurE showed quasi-reversible acid-mediated inactivation, but wt AaPurE was much more stable at pH 3.5, with a &gt; or = 20 degrees C higher thermal unfolding temperature at all pHs. His89 is not essential and does not function as part of a proton relay system. The kcat pH-rate profile was consistent with the assignment of pK1 to unproductive protonation of bound nucleotide and pK2 to deprotonation of His59. A 1.85 A resolution crystal structure of the inactive mutant H59N-AaPurE soaked in CAIR showed that protonation of CAIR C4 can occur in the absence of His59. The resulting species, modeled as isoCAIR [4(R)-carboxy-5-iminoimidazoline ribonucleotide], is strongly stabilized by extensive interactions with the enzyme and a water molecule. The carboxylate moiety is positioned in a small pocket proposed to facilitate nucleotide decarboxylation in the forward direction (N5-CAIR --&gt; CAIR) [Meyer, E., Kappock, T. J., Osuji, C., and Stubbe, J. (1999) Biochemistry 38, 3012-3018]. Comparisons with model studies suggest that in the reverse (nonbiosynthetic) direction PurE favors protonation of CAIR C4. We suggest that the essential role of protonated His59 is to lower the barrier to decarboxylation by stabilizing a CO2-azaenolate intermediate.

 

== References ==

[[Category: Kappock, T J]]

[[Category: Starks, C M]]

[[Category: Purine biosynthesis]]