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A sucrose‐binding site provides a lead towards an isoform‐specific inhibitor of the cancer‐associated enzyme carbonic anhydrase IX
Author(s) -
Pinard Melissa A.,
Aggarwal Mayank,
Mahon Brian P.,
Tu Chingkuang,
McKenna Robert
Publication year - 2015
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 37
ISSN - 2053-230X
DOI - 10.1107/s2053230x1501239x
Subject(s) - active site , chemistry , biochemistry , enzyme , carbonic anhydrase , gene isoform , mutagenesis , binding site , stereochemistry , mutant , gene
Human carbonic anhydrase (CA; EC 4.2.1.1) isoform IX (CA IX) is an extracellular zinc metalloenzyme that catalyzes the reversible hydration of CO 2 to HCO 3 − , thereby playing a role in pH regulation. The majority of normal functioning cells exhibit low‐level expression of CA IX. However, in cancer cells CA IX is upregulated as a consequence of a metabolic transition known as the Warburg effect. The upregulation of CA IX for cancer progression has drawn interest in it being a potential therapeutic target. CA IX is a transmembrane protein, and its purification, yield and crystallization have proven challenging to structure‐based drug design, whereas the closely related cytosolic soluble isoform CA II can be expressed and crystallized with ease. Therefore, we have utilized structural alignments and site‐directed mutagenesis to engineer a CA II that mimics the active site of CA IX. In this paper, the X‐ray crystal structure of this CA IX mimic in complex with sucrose is presented and has been refined to a resolution of 1.5 Å, an R cryst of 18.0% and an R free of 21.2%. The binding of sucrose at the entrance to the active site of the CA IX mimic, and not CA II, in a non‐inhibitory mechanism provides a novel carbohydrate moiety binding site that could be further exploited to design isoform‐specific inhibitors of CA IX.