Major fimbrial subunit MrkA (MrkA)

The Major fimbrial subunit MrkA is the primary structural protein of the type 3 fimbriae in Klebsiella pneumoniae, a significant Gram-negative opportunistic pathogen [1, 11]. These fimbriae are helix-shaped appendages that play a critical role in bacterial colonization by mediating adhesion to both biotic host tissues and abiotic surfaces, such as urinary catheters and endotracheal tubes [3, 4, 13]. While the associated MrkD adhesin facilitates specific binding to collagen, the MrkA shaft is the predominant factor driving the formation of dense, mature biofilms, which protect the bacteria from host immune responses and conventional antibiotic treatment [1, 6]. MrkA is highly conserved across various clinical isolates of K. pneumoniae, making it an attractive target for anti-virulence and immunotherapy strategies [7, 12]. Experimental monoclonal antibodies targeting MrkA have demonstrated the ability to inhibit biofilm formation and promote opsonophagocytic killing in preclinical models of pneumonia and sepsis [5, 10]. However, a significant therapeutic challenge is the heterogeneous expression of MrkA, as sub-populations of bacteria that do not express the fimbriae can evade antibody-mediated clearance, potentially limiting the efficacy of these treatments in certain infection stages [10, 12].

Other names

Fimbrial subunit type 3Type 3 fimbrial subunitMajor pilin MrkAMrkA fimbrial proteinPilin subunit MrkA

Inhibition of bacterial adhesion to host and abiotic surfaces, disruption of biofilm formation, and enhancement of opsonophagocytic killing by host immune cells