TatABC overexpression improves Corynebacterium glutamicum Tat-dependent protein secretion

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• The twin-arginine translocation (Tat) pathway facilitates protein secretion across the cytoplasmic membrane.
• In Corynebacterium glutamicum, the Tat system minimally comprises TatA and TatC for function, with TatB enhancing efficiency.
• Previous studies confirmed Tat pathway secretion of Chryseobacterium proteolyticum pro-protein glutaminase (pro-PG) and Streptomyces mobaraensis pro-transglutaminase (pro-TG).

Purpose of the Study:

• To investigate the impact of overexpressing Tat pathway components on pro-PG and pro-TG secretion in C. glutamicum.
• To identify potential bottlenecks in the Tat-dependent protein secretion process.

Main Methods:

• Overexpression of TatC, TatAC, and TatABC in C. glutamicum.
• Quantification of secreted pro-PG and pro-TG levels.
• Comparison of Tat pathway secretion with the Sec pathway for pro-TG.

Main Results:

• Overexpression of TatC or TatAC led to a threefold increase in secreted pro-PG.
• Further threefold increase in pro-PG secretion was observed upon TatABC overexpression.
• TatC protein amount represents the primary bottleneck, followed by TatB, in Tat-dependent secretion.
• TatABC overexpression with a TorA signal peptide resulted in higher pro-TG accumulation via the Tat pathway compared to the Sec pathway.

Conclusions:

• TatABC overexpression significantly enhances Tat-dependent secretion of pro-PG and pro-TG in C. glutamicum.
• The levels of TatC and TatB are critical limiting factors for efficient protein secretion via the Tat pathway.