The immobile soil bacteria Streptomyces exhibit a fungus mycelium-like growth. To defend themselves and their habitat against nutrient-competitors they produce a variety of bioactive secondary metabolites. S. mobaraensis produces, among others, three proteinaceous inhibitors against proteases belonging to different families. Additionally, these three inhibitors were identified as intrinsic transglutaminase-substrates (TGase) from S. mobaraensis. The objective of this work was both, the identification of the coding genes as well as a further characterization of the above mentioned proteins.

The Streptomyces papain inhibitor-coding gene (SPI) was analyzed via molecular biologic methods. The heterologous production of SPI in E. coli was successful, though despite completely different production procedures rSPI was inactive. Subsequent investigations proved that wtSPI is composed of a proteinaceous TGase substrate and a small molecule of unknown size and structure that is responsible for the protease inhibitory effect. The coding genes of Streptomyces subtilisin and TAMEP inhibitor (SSTI), dispase autolysis inducing protein (DAIP), three putative rodlins, one putative long and five putative short chaplins, the transglutaminase activating metalloprotease (TAMEP), two putative TAMEP-related metalloproteases, five putative class 1 and one putative class 2 signal peptidase were identified via complete genome sequencing and subsequent comparison with known peptides or sequences from related proteins from other Streptomyces, respectively. The following biochemical characterization of DAIP indicated an enzymatic activity, though the mechanism could not be illuminated. In silico-analysis of the structure of DAIP revealed that the protein belongs to aspartic proteases. Formally classification of SSTI belonging to Streptomyces subtilisin inhibitor-family was confirmed by the complete protein sequence. In silico-analysis of the structure of SSTI showed that the putative binding sites for TGase are located on one side of the protein whereas the binding side for subtilisin is located on the other side.