Ergosterol-binding protein

The most common proteins termed “fungal cell membrane ergosterol binding proteins” are **oxysterol-binding-protein-related proteins (ORPs)** such as Osh4/Kes1, and sterol sensor-transcription factors such as Upc2. ORPs (e.g., Osh4) mediate ergosterol transport between membranes via a hydrophobic tunnel that binds ergosterol; these proteins regulate sterol distribution, membrane structure, and cell physiology[4][5]. Upc2 senses ergosterol levels and regulates the transcription of genes required for ergosterol biosynthesis and uptake; its ergosterol-binding domain confers specificity for sterol recognition[6][1]. Ergosterol itself is the principal sterol in fungal membranes—functionally analogous to cholesterol in animals—critical for membrane integrity, permeability, and organization[2][5][7][8]. It is the direct molecular target of polyene antifungal agents (amphotericin B, nystatin), which bind ergosterol and induce lethal membrane damage, as well as the indirect target of azoles, which inhibit enzymes in the ergosterol biosynthesis pathway (notably CYP51/ERG11)[3][7]. Disruption of ergosterol binding or biosynthesis leads to loss of fungal viability and virulence[1][9][5]. The submitted target name, “Fungal cell membrane ergosterol binding protein,” is **not a unique or canonical protein name**; it is a generic descriptor encompassing multiple protein families. Most commonly, it refers to specific ergosterol-binding proteins such as **Osh4/Kes1 (oxysterol-binding), Upc2 (sterol sensor-transcription factor), or more generally to the ergosterol molecule itself as a drug target component of the membrane**[4][6][1]. For structured data, it is essential to specify the exact protein of interest. **Note:** The term provided is *generic, ambiguous, and non-canonical*. There is no single entity called “Fungal cell membrane ergosterol binding protein”; rather, multiple proteins bind ergosterol in fungi, including oxysterol-binding proteins, sterol transporter proteins, and sterol-sensing transcription factors. For accurate mapping, further specificity (e.g., “Osh4,” “Upc2,” or “CYP51/ERG11”) is required.

Other names

Oxysterol binding protein (Osh4, Kes1)Sterol-sensing proteinFungal sterol receptor (Upc2)Fungal oxysterol-binding-protein-related protein (ORP)

Polyene antifungals (e.g., amphotericin B, nystatin) directly bind ergosterol, causing membrane disruption and cell death[5][7]. Azole antifungals inhibit ergosterol biosynthesis enzymes (such as CYP51/ERG11)[3][7].