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Updated: May 8, 2026
07:32
Biolistic Transformation of a Fluorescent Tagged Gene into the Opportunistic Fungal Pathogen Cryptococcus neoformans
Published on: March 19, 2015
Restricted substrate specificity for the geranylgeranyltransferase-I enzyme in Cryptococcus neoformans: implications
Kyla Selvig1, Elizabeth R Ballou, Connie B Nichols
1Departments of Medicine, Molecular Genetics, and Microbiology, Duke University School of Medicine, Durham, North Carolina, USA.
Eukaryotic Cell
|September 10, 2013
Summary
Cryptococcus neoformans CDC43, the beta subunit of geranylgeranyltransferase-I (Ggtase-I), is vital for thermotolerance, morphogenesis, and virulence. Its function is not essential, but it impacts membrane localization of specific GTPases.
Area of Science:
- Molecular Biology
- Cell Biology
- Mycology
Background:
- Protein function relies on correct cellular localization, often achieved through prenylation of C-terminal CaaX motifs by CaaX prenyltransferases.
- Farnesyltransferase (Ftase) and geranylgeranyltransferase-I (Ggtase-I) are key enzymes in this process, with substrate specificity classically determined by the CaaX motif's terminal amino acid.
- Cryptococcus neoformans is a significant human fungal pathogen where understanding protein localization and virulence factors is crucial.
Purpose of the Study:
- To identify the gene encoding the beta subunit of Ggtase-I in Cryptococcus neoformans (CDC43).
- To investigate the role of Ggtase-I mediated activity in C. neoformans, focusing on its necessity for survival and its impact on protein localization.
- To explore the specificity of CaaX prenyltransferases in C. neoformans and their potential unique substrate recognition mechanisms.
Main Methods:
- Gene identification and knockout (cdc43Δ mutant) in Cryptococcus neoformans.
- Analysis of protein membrane localization using techniques like Western blotting or immunofluorescence.
- Assessment of fungal phenotypes including thermotolerance, morphogenesis, and virulence in the cdc43Δ mutant.
Main Results:
- The gene encoding the beta subunit of Ggtase-I was identified as CDC43.
- While Ggtase-mediated activity is not essential for survival, CDC43 is critical for thermotolerance, morphogenesis, and virulence in C. neoformans.
- Ggtase-I function is required for the full membrane localization of Rho10 and Cdc42 paralogs, but not Rac or Ras proteins, despite similar CaaL motifs.
- Membrane localization of these GTPases depends on CaaX cysteine prenylation.
Conclusions:
- Cryptococcus neoformans CDC43 plays a significant role in fungal development and pathogenicity, independent of its essentiality for basic survival.
- C. neoformans CaaX prenyltransferases exhibit unique substrate recognition patterns, diverging from established models.
- The C. neoformans Ftase may be the primary prenyltransferase for proteins typically geranylgeranylated in other organisms, suggesting a specialized prenylation landscape in this fungus.
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