Requirement of MrpH for mannose-resistant Proteus-like fimbria-mediated hemagglutination by Proteus mirabilis.
Two new genes, mrpH and mrpJ, were identified downstream of mrpG in the mrp gene cluster encoding mannose-resistant Proteus-like (MR/P) fimbriae of uropathogenic Proteus mirabilis. Since the predicted MrpH has 30% amino acid sequence identity to PapG, the Galalpha(1-4)Gal-binding adhesin of Escherichia coli P fimbriae, we hypothesized that mrpH encodes the functional MR/P hemagglutinin. MR/P fimbriae, expressed in E. coli DH5alpha, conferred on bacteria both the ability to cause mannose-resistant hemagglutination and the ability to aggregate to form pellicles on the broth surface. Both a DeltamrpH mutant expressed in E. coli DH5alpha and an isogenic mrpH::aphA mutant of P. mirabilis were unable to produce normal MR/P fimbriae efficiently, suggesting that MrpH was involved in fimbrial assembly. Amino acid residue substitution of the N-terminal cysteine residues (C66S and C128S) of MrpH abolished the receptor-binding activity (hemagglutinating ability) of MrpH but allowed normal fimbrial assembly, supporting the notion that MrpH was the functional MR/P hemagglutinin. Immunogold electron microscopy of P. mirabilis HI4320 revealed that MrpH was located at the tip of MR/P fimbriae, also consistent with its role in receptor binding. The isogenic mrpH::aphA mutant of HI4320 was less able to colonize the urine, bladder, and kidneys in a mouse model of ascending urinary tract infection (P < 0.01), and therefore MR/P fimbriae contribute significantly to bacterial colonization in mice. While there are similarities between P. mirabilis MR/P and E. coli P fimbriae, there are more notable differences: (i) synthesis of the MrpH adhesin is required to initiate fimbrial assembly, (ii) MR/P fimbriae confer an aggregation phenotype, (iii) site-directed mutation of specific residues can abolish receptor binding but allows fimbrial assembly, and (iv) mutation of the adhesin gene abolishes virulence in a mouse model of ascending urinary tract infection.
Li
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Department of Microbiology and Immunology, University of Maryland, Baltimore, Maryland 21201, USA.
Johnson
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Mobley
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HL
D018829:Adhesins, Bacterial / Q000235:genetics* / Q000502:physiology; D000368:Aged; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000235:genetics; D005260:Female; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000502:physiology*; D005798:Genes, Bacterial; D006388:Hemagglutinins / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008358:Mannose / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D011512:Proteus Infections / Q000382:microbiology*; D011513:Proteus mirabilis / Q000235:genetics / Q000502:physiology*; D011817:Rabbits; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014552:Urinary Tract Infections / Q000382:microbiology; D014774:Virulence
D018829:Adhesins, Bacterial; D004269:DNA, Bacterial; D006388:Hemagglutinins; C119575:MrpH protein, Proteus mirabilis; D036781:Fimbriae Proteins; D008358:Mannose