Ketosteroid Isomerase: Difference between revisions
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===Dimer Interface=== | ===Dimer Interface=== | ||
The biologically active unit of KSI is a 2-fold symmetric dimer in which the two chains are packed together via hydrophobic and electrostatic interactions between the "back faces" of the β-sheets. The curved β-sheets on each of the monomers expose convex faces to each other, forming well-defined interactions. In their NMR structure of KSI, Massiah et al. identified interchain hydrophobic interactions (A), as well, a number of polar residues (B) located within the dimer interface. Although they were unable to resolve interchain hydrogen-bonding interactions, they were able to resolve an intrachain hydrogen bond between His100 and Glu77 (C). The apparent pKa of His100 is 4.3, and the authors speculate that this unusually low pKa may be the result of electrostatic effects from nearby cationic residues (Arg102 and Arg113). | The biologically active unit of KSI is a 2-fold symmetric dimer in which the two chains are packed together via hydrophobic and electrostatic interactions between the "back faces" of the β-sheets. The curved β-sheets on each of the monomers expose convex faces to each other, forming well-defined interactions. In their NMR structure of KSI, Massiah et al. identified interchain hydrophobic interactions (A), as well, a number of polar residues (B) located within the dimer interface. Although they were unable to resolve interchain hydrogen-bonding interactions, they were able to resolve an intrachain hydrogen bond between His100 and Glu77 (C). The apparent pKa of His100 is 4.3, and the authors speculate that this unusually low pKa may be the result of electrostatic effects from nearby cationic residues (Arg102 and Arg113). | ||
[[Image:Massiah.png|center]] | |||
===Hydrophobic Active Site=== | ===Hydrophobic Active Site=== | ||
