Isolation and characterization of a trypsin-like protease from Trichoderma viride

A Bimodal Nanosensor for Probing Influenza Fusion Protein Activity Using Magnetic Relaxation

Viral fusion is a critical step in the entry pathway of enveloped viruses and remains a viable target for antiviral exploration. The current approaches for studying fusion mechanisms include ensemble fusion assays, high-resolution cryo-TEM, and single-molecule fluorescence-based methods. While these methods have provided invaluable insights into the dynamic events underlying fusion processes, they come with their own limitations. These often include extensive data and image analysis in addition to experimental time and technical requirements. This work proposes the use of the spin-spin T2 relaxation technique as a sensitive bioanalytical method for the rapid quantification of interactions between viral fusion proteins and lipids in real time. In this study, new liposome-coated iron oxide nanosensors (LIONs), which mimic as magnetic-labeled host membranes, are reported to detect minute interactions occurring between the membrane and influenza's fusion glycoprotein, hemagglutinin (HA). The influenza fusion protein's interaction with the LION membrane is detected by measuring changes in the sensitive spin-spin T2 magnetic relaxation time using a bench-top NMR instrument. More data is gleaned from including the fluorescent dye DiI into the LION membrane. In addition, the effects of environmental factors on protein-lipid interaction that affect fusion such as pH, time of incubation, trypsin, and cholesterol were also examined. Furthermore, the efficacy and sensitivity of the spin-spin T2 relaxation assay in quantifying similar protein/lipid interactions with more native configurations of HA were demonstrated using virus-like particles (VLPs). Shorter domains derived from HA were used to start a reductionist path to identify the parts of HA responsible for the NMR changes observed. Finally, the known fusion inhibitor Arbidol was employed in our spin-spin T2 relaxation-based fusion assay to demonstrate the application of LIONs in real-time monitoring of this aspect of fusion for evaluation of potential fusion inhibitors.

The study of intracellular and secreted high-molecular-mass protease(s) of Trichoderma spp., and their responses to conidiation stimuli

We continued our study of high-molecular-mass proteases (HMMPs) using several strains of the genus Trichoderma, and other filamentous fungi (Botrytis cinerea, Aspergillus niger, Fusarium culmorum, and Penicillium purpurogenum). We found that five Trichoderma strains secreted HMMPs into the media after induction with bovine serum albumin. Botrytis cinerea and F. culmorum secreted proteases in the absence of inducer, while A. niger or P. purpurogenum did not secrete proteolytic activity (PA). The activity of HMMPs secreted by or intracellularly located in Trichoderma spp. represents the predominant part of cellular PA, according to zymogram patterns. This observation allowed the study of HMMPs' physiological role(s) independent from the secretion. In studying conidiation, we found that illumination significantly stimulated PA in Trichoderma strains. In the T. atroviride IMI 206040 strain, we demonstrated that this stimulation is dependent on the BLR1 and BLR2 receptors. No stimulation of PA was observed when mechanical injury was used as an elicitor of conidiation. Compounds used as inhibitors or activators of conidiation exerted no congruent effects on both PA and conidiation. These results do not favour a direct role of HMMPs in conidiation. Probably, HMMP activity may be involved in the process of the activation of metabolism during vegetative growth, differentiation, and aging-related processes.

Purification and Biochemical Characterization of a Neutral Serine Protease from Trichoderma harzianum. Use in Antibacterial Peptide Production from a Fish By-Product Hydrolysate

This study reports the purification and biochemical characterization of an extracellular neutral protease from the fungus Trichoderma harzianum. The protease (Th-Protease) was purified from the culture supernatant to homogeneity by a three-step procedure with 14.2% recovery and 9.06-fold increase in specific activity. The purified enzyme appeared as a single protein band after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with a molecular mass of about 20 kDa. The optimum pH and temperature for the proteolytic activity were pH 7.0 and 40 °C, respectively. The enzyme was then investigated for its potential application in the production of antibacterial peptides. Interestingly, Scorpaena notata viscera protein hydrolysate prepared using the purified serine protease (Th-Protease) showed remarkable in vitro antibacterial activities. A peptide with a high antibacterial activity was further purified by a three-step procedure, and its sequence was identified as FPIGMGHGSRPA. The result of this study offers a promising alternative to produce natural antibacterial peptides from fish protein hydrolysate.

Properties of secreted protease from vegetative Trichoderma atroviride mycelia cultivated with protein inducer reveal a complex protein-recognition mechanism

In this study, the submerged cultivation of Trichoderma atroviride with protein substrate (bovine serum albumin, casein, ovalbumin, etc.) led to the secretion of protease activity (PA) into the medium. The secretion started within 30 h and rose to the maximum after 72-h cultivation. It continued upon the prolonged cultivation (up to 8 days) with lower secreted PA. Zymography of the secreted protease (SDS-PAGE with 0.2% gelatine), revealing high molecular weight (m.w.) protease(s) (~200 kDa) with high autolytic activity as the only secretory product. Enzymological characteristics of high m.w. proteases elicited by different inducer proteins were surprisingly different, suggesting that mycelia can recognize not only the presence of inducer proteins but also some qualitative characteristics. Low m.w. protease(s), as found from other studies was(were) seen after prolonged cultivation only, as a band with m.w. about 36 kDa. Expression of known Trichoderma spp. genes encoding secreted proteases, prb1 and proA, showed that only prb1 was expressed after 3-4 days of cultivation, i.e., after the early-secretion phase. The secretory activity of the earlier phase was impaired by tunicamycin and brefeldin A and was significantly stimulated by uncoupler. The existence of a biphasic fungal secretory response and the protein quality recognition represent previously unrecognized processes.

Purification and preliminary characterization of a cold-adapted extracellular proteinase from Trichoderma atroviride

Eleven cold-tolerant Trichoderma isolates were screened for the production of proteolytic activities at 10 degrees C. Based on the activity profiles determined with paranitroanilide substrates at 5 degrees C, strain T221 identified as Trichoderma atroviride was selected for further investigations. The culture broth of the strain grown at 10 degrees C in casein-containing culture medium was concentrated by lyophilization and subjected to gel filtration, which was followed by chromatofocusing of the fraction showing the highest activity on N-benzoyl-Phe-Val-Arg-paranitroanilide. The purified enzyme had a molecular weight of 24 kDa, an isoelectric point of 7.3 and a pH optimum of 6.2. The temperature optimum of 25 degrees C and the low thermal stability suggested that it is a true cold-adapted enzyme. Substrate specificity data indicate that the enzyme is a proteinase with a preference for Arg or Lys at the P1 position. The effect of proteinase inhibitors suggests that the enzyme has a binding pocket similar to the one present in trypsin.

Proteomic analysis of secreted proteins from Trichoderma harzianum

Trichoderma mycoparasitic activity depends on the secretion of complex mixtures of hydrolytic enzymes able to degrade the host cell wall. We have analysed the extracellular proteome secreted by T. harzianum CECT 2413 in the presence of different fungal cell walls. Significant differences were detected in 2DE maps, depending on the use of specific cell walls or chitin. A combination of MALDI-TOF and liquid chromatography mass spectrometry allowed the identification of a novel aspartic protease (P6281: MW 33 and pI 4.3) highly induced by fungal cell walls. A broad EST library from T. harzianum CECT 2413 was used to obtain the full-length sequence. The protein showed 44% identity with the polyporopepsin (EC 3.4.23.29) from the basidiomycete Irpex lacteus. Lower identity percentages were found with other pepsin-like proteases from filamentous fungi (<31%) and animals (<29%). Northern blot and promoter sequence analyses support the implication of the protease P6281 in mycoparasitism.

Extracellular proteases of Trichoderma species. A review

Cellulolytic, xylanolytic, chitinolytic and beta-1,3-glucanolytic enzyme systems of species belonging to the filamentous fungal genus Trichoderma have been investigated in details and are well characterised. The ability of Trichoderma strains to produce extracellular proteases has also been known for a long time, however, the proteolytic enzyme system is relatively unknown in this genus. Fortunately, in the recent years more and more attention is focused on the research in this field. The role of Trichoderma proteases in the biological control of plant pathogenic fungi and nematodes has been demonstrated, and it is also suspected that they may be important for the competitive saprophytic ability of green mould isolates and may represent potential virulence factors of Trichoderma strains as emerging fungal pathogens of clinical importance. The aim of this review is to summarize the information available about the extracellular proteases of Trichoderma. Numerous studies are available about the extracellular proteolytic enzyme profiles of Trichoderma strains and about the effect of abiotic environmental factors on protease activities. A number of protease enzymes have been purified to homogeneity and some protease encoding genes have been cloned and characterized. These results will be reviewed and the role of Trichoderma proteases in biological control as well as their advantages and disadvantages in biotechnology will be discussed.