Proteomics studies in Trichoderma reesei

Proteome analysis is the simultaneous examination of a large subset of the protein species in a given cell. Traditionally proteomics is performed by two-dimensional gel electrophoresis combined with protein identification by mass spectrometry. We have set up proteomics methodology for the analysis of both extracellular and intracellular proteins of Trichoderma reesei. We use 2-D gel electrophoresis at different pI ranges accompanied with staining with silver stain or the fluorescent dye Sybro ruby. Also protein samples from in vivo labelling with 35S-methionine have been analysed to obtain more sensitivity and to study the synthesis rates of different proteins. Moreover, we have used antibodies against phosphoserine, phosphothreonine and phosphotyrosine to reveal changes in protein phosphorylation. The major cellulases produced by T. reesei can be readily recognised in 2-D gels run from both extracellular and intracellular samples. The cellulases, as most extracellular proteins are secreted from T. reesei as multiple pI forms. Deglycosylation of the proteins, e.g. the major cellulase CBHI, turns the protein into a single pI form, showing that the pI heterogeneity resides in the glycans. Our proteomics studies from intracellular samples have mostly been focused on analysis of secretion stress, i.e. the effects of compromised protein folding, processing or transport in cells producing heterologous protein or cells exposed to inhibitors of the secretory functions. These studies have pointed out a large number of protein spots affected by secretion stress. Major differences in the protein phosphorylation patterns also occur in these experimental conditions.