Identification of new secreted proteins and secretion of heterologous amylase by C. glutamicum

In this study, secreted Corynebacterium glutamicum proteins were investigated by two-dimensional gel electrophoresis. Around 100 spots observed in the pH range 4.5-5.5 had molecular masses that varied from 10 to 50 kDa. Upon N-terminal amino acid sequence analysis by Edman degradation, two of them were hits to two hypothetical proteins encoded by cgR-1176 and cgR-2070 on C. glutamicum R genome, respectively. Active-form α-amylase derived from Geobacillus stearothermophilus was successfully secreted by using the predicted cgR-1176 and cgR-2070 signal sequences, indicating that these hypothetical proteins were secreted proteins. Analysis using a disruption mutant of the twin-arginine translocation (Tat) export pathway machinery of C. glutamicum suggested that one is Tat pathway dependent secretion while the other is independent of the pathway. Our results demonstrate that C. glutamicum can secrete exoproteins by using its own signal sequences, indicating its potential as a host for protein productions.