# Towards Understanding the Function of Aegerolysins
## 2 Aegerolysins
### Fungal Aegerolysins from Ascomycotta--Eurotimyetes
#### 2.2.3 Aegerolysins from _Aspergillus terreus_  
_Aspergillus terreus_ [PERSON] (1918) (_Eurotiales_) is a filamentous fungus found in soil worldwide. Although it was thought to be purely asexual, it is now known to be capable of sexual reproduction. This saprotrophic fungus is common in warmer climates such as the tropics and subtropics. It is found not only in soil, but also in habitats, such as decomposingvegetation and dust [21]. _A. terreus_ is used in industry to produce important organic acids, such as itaconic acid, and enzymes. It was also the original source of the drug mevinolin (lovastatin), which is used to lower serum cholesterol. It can cause opportunistic infections in people with weakened immune systems [28].  
Terrelysin (**Ter**) is an aegerolysin from _A. terreus_. The genome sequence was used to identify the **Ter** sequence based on homology with other known aegerolysins [28]. The recombinant protein **rTer** was purified and its mass of about 16 kDa was determined by MALDI TOF MS [28]. Circular dichroism analysis shows that the secondary structure of the protein is predominantly \(\beta\)-sheet. Thermal denaturation results of **rTer** show that the protein retains the \(\beta\)-sheet confirmation up to 65 \({}^{\circ}\)C. Clinical identification of _A. terreus_ in aspergillosis is limited to broad identification of lesions in affected organs by biopsy, radiological methods, or detection of fungal carbohydrates, which often does not allow species-specific identification. Due to the urgent need for diagnostic methods that allow early and specific identification of the pathogen, monoclonal antibodies to cytolytic hyphal exoantigens were generated [116]. Additionally, specific monoclonal antibodies against **rTer** were developed and used to quantify the native protein in hyphal and secretion fractions grown in liquid culture at various time points [28]. Time-course studies showed that **Ter** expression was highest during early hyphal growth and decreased dramatically after mycelial expansion [117]. Immunolocalization studies showed that **Ter** was not only localized in the cytoplasm of the hyphae, but was also present in greater amounts at the tip of the hyphae [117]. By ELISA, it was found that the highest concentrations of **Ter** were found in the culture supernatant during the early stages of hyphal growth, compared to later time points when hyphal growth and apical elongation were reduced. Because **Ter** does not possess a signal peptide, it was suggested that it might diffuse or be actively secreted during initial hyphal growth (i.e., apical elongation) by other, yet uncharacterized, processes [117]. These results were confirmed in cultures grown at both room temperature and 37 \({}^{\circ}\)C. These observations suggest that **Ter** may be a potential biomarker for _A. terreus_ infections [117].  
There is no MACPF-like partner protein gene encoded alongside the _ter_ gene [92]. There are some differences in sequences around the putative intron splice site and at the C-terminus between **rTer** from ATCC 1012 and the genome sequences of NIH2624 (ASM14961) and IFO6365.