Multiple proteins encoded within the urease gene complex of Proteus mirabilis

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Uropathogenic Proteus mirabilis is a significant cause of urinary tract infections.
• Urease activity in P. mirabilis contributes to virulence and pathogenesis.
• Understanding the genetic basis of urease production is crucial for developing targeted therapies.

Purpose of the Study:

• To clone and characterize the urease gene complex from a uropathogenic P. mirabilis strain.
• To identify the specific genes and proteins involved in urease activity.
• To elucidate the roles of individual urease isozymes in enzyme function.

Main Methods:

• Construction of a genomic library of P. mirabilis in Escherichia coli using cosmid vector pHC79.
• Screening for urease-positive recombinant clones.
• Plasmid manipulation and subcloning to isolate the urease gene complex (pSKW4).
• Construction of insertion mutations in genes encoding urease-associated proteins.

Main Results:

• A 10.2-kilobase plasmid (pSKW4) encoding three urease isozymes was isolated.
• Seven proteins (68K, 28K, 25K, 22.5K, 18.5K, 7.5K, and 5.2K) were identified within the urease gene complex.
• Mutations in genes for 68K, 28K, 25K, 22.5K, 7.5K, and 5.2K proteins abolished or reduced urease activity.
• Inactivation of the 18.5K protein gene did not affect urease activity.

Conclusions:

• The P. mirabilis urease gene complex comprises at least seven genes.
• Proteins 68K, 28K, 25K, 22.5K, 7.5K, and 5.2K are essential for urease activity.
• The 18.5K protein is not required for urease function, suggesting a regulatory or accessory role.