4L7K

Crystal Structure of Ketosteroid Isomerase D38E from Pseudomonas Testosteroni (tKSI)

Summary for 4L7K

• Entry DOI: 10.2210/pdb4l7k/pdb
• Descriptor: Steroid Delta-isomerase, GLYCEROL, SULFATE ION, ... (4 entities in total)
• Functional Keywords: isomerase
• Biological source: Comamonas testosteroni
• Total number of polymer chains: 12
• Total formula weight: 166473.22

Authors

Gonzalez, A.,Tsai, Y.,Schwans, J.,Sunden, F.,Herschlag, D. (deposition date: 2013-06-14, release date: 2013-07-03, Last modification date: 2024-02-28)

Primary citation

Schwans, J.P.,Sunden, F.,Lassila, J.K.,Gonzalez, A.,Tsai, Y.,Herschlag, D.
Use of anion-aromatic interactions to position the general base in the ketosteroid isomerase active site.
Proc.Natl.Acad.Sci.USA, 110:11308-11313, 2013

PubMed Abstract: Although the cation-pi pair, formed between a side chain or substrate cation and the negative electrostatic potential of a pi system on the face of an aromatic ring, has been widely discussed and has been shown to be important in protein structure and protein-ligand interactions, there has been little discussion of the potential structural and functional importance in proteins of the related anion-aromatic pair (i.e., interaction of a negatively charged group with the positive electrostatic potential on the ring edge of an aromatic group). We posited, based on prior structural information, that anion-aromatic interactions between the anionic Asp general base and Phe54 and Phe116 might be used instead of a hydrogen-bond network to position the general base in the active site of ketosteroid isomerase from Comamonas testosteroni as there are no neighboring hydrogen-bonding groups. We have tested the role of the Phe residues using site-directed mutagenesis, double-mutant cycles, and high-resolution X-ray crystallography. These results indicate a catalytic role of these Phe residues. Extensive analysis of the Protein Data Bank provides strong support for a catalytic role of these and other Phe residues in providing anion-aromatic interactions that position anionic general bases within enzyme active sites. Our results further reveal a potential selective advantage of Phe in certain situations, relative to more traditional hydrogen-bonding groups, because it can simultaneously aid in the binding of hydrophobic substrates and positioning of a neighboring general base.

PubMed: 23798413
DOI: 10.1073/pnas.1206710110

Experimental method

X-RAY DIFFRACTION (2.1 Å)