Related Experiment Video

Updated: Jun 18, 2026

Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092
08:53

Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092

Published on: October 2, 2017

Functional characterization and localization of Pneumocystis carinii lanosterol synthase

Tiffany M Joffrion1, Margaret S Collins, Thomas Sesterhenn

  • 1Department of Internal Medicine, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0560, USA. joffritm@mail.uc.edu

Eukaryotic Cell
|November 10, 2009
PubMed

Insights

Pneumocystis fungi, which cause pneumonia in immunocompromised individuals, possess a unique sterol biosynthesis pathway. Researchers used yeast to demonstrate that the Pneumocystis carinii lanosterol synthase enzyme functions and localizes to lipid particles.

Area of Science:

  • Mycology
  • Fungal Pathogenesis
  • Biochemistry

Background:

  • Organisms in the genus Pneumocystis are opportunistic fungal pathogens causing lethal pneumonia in immunocompromised hosts.
  • Pneumocystis spp. uniquely lack ergosterol in their cell membranes, challenging traditional understanding of fungal sterol acquisition.
  • Transcriptional data suggests Pneumocystis carinii encodes genes involved in sterol biosynthesis, necessitating further investigation into this pathway.

Purpose of the Study:

  • To investigate the function and cellular localization of the Pneumocystis carinii lanosterol synthase (ERG7) enzyme.
  • To understand the sterol pathway in the uncultivable Pneumocystis fungi.
  • To validate the utility of a yeast heterologous system for studying Pneumocystis sterol biosynthesis.

Main Methods:

  • Utilized yeast deletion strains (Saccharomyces cerevisiae ERG7-null mutant) to express and analyze P. carinii lanosterol synthase (PcErg7p).
  • Employed gas chromatographic analysis to detect and quantify lanosterol production.
  • Applied Western blotting and fluorescence microscopy to determine PcErg7p localization in yeast and P. carinii.

Main Results:

  • Expression of PcErg7p in yeast produced functional lanosterol synthase, with comparable lanosterol levels to the native yeast enzyme.
  • PcErg7p localized to lipid particles in yeast, similar to the endogenous yeast Erg7p.
  • Lipid particles were observed in P. carinii for the first time, with PcErg7p localized to these structures, indicating a conserved function.

Conclusions:

  • The P. carinii lanosterol synthase (PcErg7p) is functional and localizes to lipid particles, suggesting a conserved role in sterol biosynthesis.
  • The study provides strong evidence for an active sterol pathway in P. carinii.
  • A yeast heterologous system is a valuable tool for future research into the Pneumocystis sterol pathway.

More Related Videos

Identification of Plasmodesmal Localization Sequences in Proteins In Planta08:07

Identification of Plasmodesmal Localization Sequences in Proteins In Planta

Published on: August 15, 2017

Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/4306:06

Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43

Published on: September 11, 2020

Related Concept Videos

Formation of Lipopolysaccharides01:19

Formation of Lipopolysaccharides

Lipopolysaccharides (LPS) are crucial components of the outer membrane of Gram-negative bacteria, serving both structural and functional roles. It contributes to membrane stability and protects bacteria from host immune responses. LPS is composed of three major regions—lipid A, a core oligosaccharide, and an O antigen. The biosynthesis and assembly of LPS involve a highly coordinated set of enzymatic reactions and transport mechanisms. Additionally, LPS is recognized as an endotoxin, triggering...
Regulation of Nuclear Protein Sorting01:45

Regulation of Nuclear Protein Sorting

Nuclear protein sorting regulates nucleus composition and gene expression, crucial for determining the fate of a eukaryotic cell. Hence, the entry and exit of molecules across the nuclear envelope is a tightly controlled process. Nuclear protein sorting can be inhibited by one of the following ways: 1) masking cargo signal sequences, 2) modifying the nuclear receptor's affinity for cargo, 3) controlling the nuclear pore size, 4) retaining the cargo during its transit to the cytosol or the...
Ligand Binding and Linkage00:49

Ligand Binding and Linkage

Allosteric proteins have more than one ligand binding site; the binding of a ligand to any of these sites influences the binding of ligands to the other sites. When a protein is allosteric, its binding sites are called coupled or linked.  In the case of enzymes, the site that binds to the substrate is known as the active site and the other site is known as the regulatory site. When a ligand binds to the regulatory site, this leads to conformational changes in the protein that can influence the...
Polymer Classification: Stereospecificity01:26

Polymer Classification: Stereospecificity

Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...
Protein Import into the Peroxisomes01:27

Protein Import into the Peroxisomes

Cells contain membrane-bound organelles called peroxisomes that oxidize organic molecules by transferring hydrogen atoms to oxygen, producing hydrogen peroxide. Peroxisomes enzymatically convert the released hydrogen peroxide into water and oxygen.
Peroxisomal Protein Import:
Peroxisomes lack the genetic machinery required to code for their own proteins. Hence, most peroxisomal membrane, lumenal and transmembrane proteins are synthesized in the cytoplasm or ER and transported to the peroxisome...
Allosteric Proteins-ATCase01:19

Allosteric Proteins-ATCase

Binding sites linkages can regulate a protein's function.  For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to  N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...