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Crystal Structures of Candida albicans Phosphodiesterase 2 and Implications for Its Biological Functions.

ABSTRACT: The cAMP signaling system plays important roles in the physiological processes of pathogen yeast Candida albicans, but its functional mechanism has not been well illustrated. Here, we report the enzymatic characterization and crystal structures of C. albicans phosphodiesterase 2 (caPDE2) in the unliganded and 3-isobutyl-1-methylxanthine-complexed forms. caPDE2 is a monomer in liquid and crystal states and specifically hydrolyzes cAMP with a K_M of 35 nM. It does not effectively hydrolyze cGMP as shown by the 1.32 × 10⁵-fold specificity of cAMP/cGMP. The crystal structure of caPDE2 shows significant differences from those of human PDEs. First, the N-terminal fragment of caPDE2 (residues 1-201) tightly associates with the catalytic domain to form a rigid molecular entity, implying its stable molecular conformation for C. albicans to resist environmental stresses. Second, the M-loop, a critical fragment for binding of the substrate and inhibitors to human PDEs, is not a part of the caPDE2 active site. This feature of caPDE2 may provide a structural basis for the design of selective inhibitors for the treatment of yeast infection.

SUBMITTER: Yao T

PROVIDER: S-EPMC9364965 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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Crystal Structures of Candida albicans Phosphodiesterase 2 and Implications for Its Biological Functions.

Yao Ting T Huang Yiyou Y Zhang Meng M Chen Yujuan Y Pei Hairun H Shi Jianyou J Wang Huanchen H Wang Yousheng Y Ke Hengming H

Biochemistry 20181004 42

The cAMP signaling system plays important roles in the physiological processes of pathogen yeast Candida albicans, but its functional mechanism has not been well illustrated. Here, we report the enzymatic characterization and crystal structures of C. albicans phosphodiesterase 2 (caPDE2) in the unliganded and 3-isobutyl-1-methylxanthine-complexed forms. caPDE2 is a monomer in liquid and crystal states and specifically hydrolyzes cAMP with a K<sub>M</sub> of 35 nM. It does not effectively hydroly ...[more]

PMID: 30231198

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Project description:BackgroundThe pathogenic yeast Candida albicans can proliferate in environments with different carbon dioxide concentrations thanks to the carbonic anhydrase CaNce103p, which accelerates spontaneous conversion of carbon dioxide to bicarbonate and vice versa. Without functional CaNce103p, C. albicans cannot survive in atmospheric air. CaNce103p falls into the β-carbonic anhydrase class, along with its ortholog ScNce103p from Saccharomyces cerevisiae. The crystal structure of CaNce103p is of interest because this enzyme is a potential target for surface disinfectants.ResultsRecombinant CaNce103p was prepared in E. coli, and its crystal structure was determined at 2.2 Å resolution. CaNce103p forms a homotetramer organized as a dimer of dimers, in which the dimerization and tetramerization surfaces are perpendicular. Although the physiological role of CaNce103p is similar to that of ScNce103p from baker's yeast, on the structural level it more closely resembles carbonic anhydrase from the saprophytic fungus Sordaria macrospora, which is also tetrameric. Dimerization is mediated by two helices in the N-terminal domain of the subunits. The N-terminus of CaNce103p is flexible, and crystals were obtained only upon truncation of the first 29 amino acids. Analysis of CaNce103p variants truncated by 29, 48 and 61 amino acids showed that residues 30-48 are essential for dimerization. Each subunit contains a zinc atom in the active site and displays features characteristic of type I β-carbonic anhydrases. Zinc is tetrahedrally coordinated by one histidine residue, two cysteine residues and a molecule of β-mercaptoethanol originating from the crystallization buffer. The active sites are accessible via substrate tunnels, which are slightly longer and narrower than those observed in other fungal carbonic anhydrases.ConclusionsCaNce103p is a β-class homotetrameric metalloenzyme composed of two homodimers. Its structure closely resembles those of other β-type carbonic anhydrases, in particular CAS1 from Sordaria macrospora. The main differences occur in the N-terminal part and the substrate tunnel. Detailed knowledge of the CaNce103p structure and the properties of the substrate tunnel in particular will facilitate design of selective inhibitors of this enzyme.

Dataset Information

Crystal Structures of Candida albicans Phosphodiesterase 2 and Implications for Its Biological Functions.

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Crystal Structures of Candida albicans Phosphodiesterase 2 and Implications for Its Biological Functions.

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