'''Crystal structure of TT0310 protein from Thermus thermophilus HB8'''
===Crystal structure of TT0310 protein from Thermus thermophilus HB8===
==Overview==
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Hot dog fold proteins sharing the characteristic "hot dog" fold are known to involve certain coenzyme A binding enzymes with various oligomeric states. In order to elucidate the oligomerization-function relationship of the hot dog fold proteins, crystal structures of the phenylacetate degradation protein PaaI from Thermus thermophilus HB8 (TtPaaI), a tetrameric acyl-CoA thioesterase with the hot dog fold, have been determined and compared with those of other family members. In the liganded crystal forms with coenzyme A derivatives, only two of four intersubunit catalytic pockets of the TtPaaI tetramer are occupied by the ligands. A detailed structural comparison between several liganded and unliganded forms reveals that a subtle rigid-body rearrangement of subunits within 2 degrees upon binding of the first two ligand molecules can induce a strict negative cooperativity to prevent further binding at the remaining two pockets, indicating that the so-called "half-of-the-sites reactivity" of oligomeric enzymes is visualized for the first time. Considering kinetic and mutational analyses together, a possible reaction mechanism of TtPaaI is proposed; one tetramer binds only two acyl-CoA molecules with a novel asymmetric induced-fit mechanism and carries out the hydrolysis according to a base-catalyzed reaction through activation of a water molecule by Asp48. From a structural comparison with other family members, it is concluded that a subgroup of the hot dog fold protein family, referred to as "asymmetric hot dog thioesterases" including medium chain acyl-CoA thioesterase II from Escherichia coli and human thioesterase III, might share the same oligomerization mode and the asymmetric induced-fit mechanism as observed in TtPaaI.
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==About this Structure==
==About this Structure==
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[[Category: Structural genomic]]
[[Category: Structural genomic]]
[[Category: Thioesterase]]
[[Category: Thioesterase]]
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Revision as of 02:29, 29 July 2008
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A novel induced-fit reaction mechanism of asymmetric hot dog thioesterase PAAI., Kunishima N, Asada Y, Sugahara M, Ishijima J, Nodake Y, Sugahara M, Miyano M, Kuramitsu S, Yokoyama S, Sugahara M, J Mol Biol. 2005 Sep 9;352(1):212-28. PMID:16061252
