Abstract
Pseudomonas aeruginosa, an important human pathogen, is estimated to be responsible for ∼10% of nosocomial infections worldwide. The pathogenesis of P. aeruginosa starts from its colonization in the damaged tissue or medical devices (e.g. catheters, prothesis and implanted heart valve etc.) facilitated by several extracellular adhesive factors including fimbrial pili. Several clusters containing fimbrial genes have been previously identified on the P. aeruginosa chromosome and named cup [1]. The assembly of the CupB pili is thought to be coordinated by two chaperones, CupB2 and CupB4. However, due to the lack of structural and biochemical data, their chaperone activities remain speculative. In this study, we report the 2.5 Å crystal structure of P. aeruginosa CupB2. Based on the structure, we further tested the binding specificity of CupB2 and CupB4 towards CupB1 (the presumed major pilus subunit) and CupB6 (the putative adhesin) using limited trypsin digestion and strep-tactin pull-down assay. The structural and biochemical data suggest that CupB2 and CupB4 might play different, but not redundant, roles in CupB secretion. CupB2 is likely to be the chaperone of CupB1, and CupB4 could be the chaperone of CupB4:CupB5:CupB6, in which the interaction of CupB4 and CupB6 might be mediated via CupB5.
Highlights
Pseudomonas aeruginosa, a gram-negative, rod-shaped bacterium, is an important opportunistic human pathogen [2]
Using limited trypsin digestion and strep-Tactin pull-down, we found that CupB2 is likely to be the chaperone of CupB1, but not CupB6
Overall structure of CupB2 The structure of P. aeruginosa CupB2 was determined to 2.5 Aby molecular replacement using SafB and PapD as search templates (Figure 1B)
Summary
Pseudomonas aeruginosa, a gram-negative, rod-shaped bacterium, is an important opportunistic human pathogen [2]. Recent statistics shows that P. aeruginosa is among the top five infective agents in the hospital, especially in the intensive care departments, responsible for nearly 10% of the hospital-acquired infections such as respiratory tract, blood, urinary tract, ear, skin and soft tissue infections [3,4,5]. The prevalence of the P. aeruginosa infections might stem from two major reasons: low antibiotics susceptibility and high ability to grow in nearly any natural and artificial surfaces. The organism is known as the most frequent colonizer of medical devices (e.g. catheters) causing cross infection in hospital and clinics. Colonization of human tissues, abiotic surfaces such as medical devices, and subsequent development into bacterial biofilm play important roles in the pathogenesis of P. aeruginosa [6,7]
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