Figure 1.

Fungal protein expression and protein secretion. Expression and secretion of proteins in filamentous fungi involve a set of important steps, starting with transcription of the protein encoding gene in the nucleus, transport of the mRNA to the ribosomes in the cytoplasm, polypeptide transfer from ribosomes to the endoplasmic reticulum (ER), protein folding and modification in ER, and further transfer of the folded proteins in vesicles to the Golgi apparatus, where they are further glycosylated and from there transferred through the outer membrane to the exterior. Peptides are produced by specific enzymes (non-ribosomal peptide synthases) in the cytoplasm and transferred to the exterior with the same protein secretion pathway as ribosomal produced proteins.