Protease-associated import systems are widespread in Gram-negative bacteria

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• Bacteria require sophisticated nutrient uptake systems for growth.
• Gram-negative plant pathogens like Pectobacterium utilize a ferredoxin uptake system (Fus) to acquire iron from host plants.
• The Fus system involves proteins for ferredoxin transport and proteolytic processing.

Purpose of the Study:

• To investigate the prevalence of ferredoxin uptake systems (Fus) in bacteria.
• To structurally and biochemically characterize homologous proteins (YddB and PqqL) from Escherichia coli.
• To determine if these E. coli proteins are analogous to components of the Pectobacterium Fus system.

Main Methods:

• Structural characterization of YddB and PqqL.
• Biochemical assays to determine protein function.
• Comparative analysis of protein structures and functions with known Fus components.

Main Results:

• Gene clusters related to the Fus system are widespread in bacterial species.
• The E. coli membrane protein YddB shares structural similarities with the outer membrane ferredoxin transporter FusA.
• The E. coli protein PqqL functions as an active protease analogous to FusC, with iron-dependent expression and specific structural features distinguishing it within the M16 protease family.

Conclusions:

• Protease-associated import systems analogous to the ferredoxin uptake system (Fus) are common in Gram-negative bacteria.
• YddB and PqqL represent functional and structural homologs of the Pectobacterium Fus system components.
• This suggests a conserved mechanism for nutrient acquisition across diverse bacterial species.