Actinobacillus seminis Secretes a Metalloprotease That Degrades Bovine Fibrinogen and IgG

Actinobacillus seminis is a Gram-negative bacterium member of the Pasteurellaceae family. Even though it is part of the ovine microbiota it is also the causal agent of genital organs affections, particularly epididymitis and orchitis. Infections caused by this microorganism generate economic losses to the ovine industry due to impaired fertility and sterility in affected animals. Knowledge about virulence factors expressed by A. seminis is scarce. In the present work, we describe the expression of a metalloprotease secreted by A. seminis that can degrade bovine fibrinogen and immunoglobulin G and present homology with a carboxy-terminal protease from A. seminis. This metalloprotease presents an optimal activity at a pH between 6 and 7, is stable up to 60°C, inactive at higher temperatures, and completely inhibited by 30 mM EDTA. The expression of this proteolytic activity is controlled by temperature, calcium, and iron. Proteases degrading extracellular matrix components and molecules involved in the immune response could facilitate and improve host colonization and invasion by A. seminis