Sandbox Reserved 914: Difference between revisions
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== Structure == | == Structure == | ||
The secondary structure of PPT1 contains several α-helices and few β-sheets. | The secondary structure of PPT1 contains several α-helices and few β-sheets. PPT1 includes residues 28-306, after the 27-residue signal peptide has been removed. There is a large insertion between β6 and β7, residues 140-223, and that forms a second domain that is compromised almost entirely of the fatty acid binding site. This second domain region contains six helices, α2-α7. | ||
=== α/β Hydrolase Fold === | === α/β Hydrolase Fold === | ||
The α/β Hydrolase Fold is common to many other hydrolases. | The α/β Hydrolase Fold is common to many other hydrolases. The α/β hydrolase fold has a central 6 stranded parallel β-sheet consisting of <scene name='57/573128/4/1'>β3-β8</scene> and α-helices <scene name='57/573128/5/1'>αA, αB, αC, and αF</scene>. It also consists of a catalytic triad and an oxyanion hole. The pKa of the nucleophile in the catalytic triad is lowered to allow the nucleophilic attack. None of the enzymes within the α/β hydrolase fold family require a cofactor for catalytic activity. | ||
=== Catalytic Triad === | === Catalytic Triad === | ||
The <scene name='57/573128/2/1'>catalytic triad</scene> is composed of Ser115, His289, and Asp233, which is the same as the catalytic triad in chymotrypsin. | The <scene name='57/573128/2/1'>catalytic triad</scene> is composed of Ser115, His289, and Asp233, which is the same as the catalytic triad in chymotrypsin. | ||
A water molecule is occupying the <scene name='57/573128/7/1'>oxyanion hole</scene> and it is hydrogen bonded to | A water molecule is occupying the <scene name='57/573128/7/1'>oxyanion hole</scene> and it is hydrogen bonded to Ser115. | ||
===Hydrophobic Groove === | ===Hydrophobic Groove === | ||
The <scene name='57/573128/3/1'>hydrophobic binding groove</scene> is located in the second domain of PPT1, where palmitate mainly binds. The fact that palmitate has to <scene name='57/573128/6/1'>bend</scene> to fit into the binding pocket suggests that this pocket is designed to bind an unsaturated fatty acid. | The <scene name='57/573128/3/1'>hydrophobic binding groove</scene> is located in the second domain of PPT1, where palmitate mainly binds. The fact that palmitate has to <scene name='57/573128/6/1'>bend</scene> to fit into the binding pocket suggests that this pocket is designed to bind an unsaturated fatty acid, with a possible cis-double bond between C4 and C5. The top portion of the groove is formed by the residues from α2 to α3. Several residues that are present near the active site create the rest of the groove, including Ile235, Val236, Gln116, Gly40, and Met41. | ||
== Function == | == Function == | ||
