Hemin Acquisition in Bartonella quintana

<p><i>Bartonella quintana</i>, a Gram-negative bacterial pathogen, causes Trench fever, bacillary angiomatosis and endocarditis. Transmitted by the human body louse (<i>Pediculus humanus corporis</i>), the agent has a tropism for erythrocytes in humans. <i>In vitro</i> growth requires an extraordinary concentration of hemin, and genomic analyses indicate several potential uptake systems and iron-responsive regulators. Transcription of the <i>hbp</i> genes (hemin binding protein genes) is responsive to alterations in available hemin and an HbpA homolog in <i>B. henselae</i> reportedly functions as a hemin receptor in <i>E. coli hemA</i> strain EB53. <i>B. quintana hbpA</i> was not able to complement EB53, indicating that it is not a hemin receptor. A functional hemin receptor and coordinate uptake system is encoded by the hemin utilization (<i>hut</i>) locus. <i>B. quintana hutA</i> was able to complement a <i>hemA</i> mutation in <i>E. coli </i>EB53 and was shown to be TonB-dependent using an isogenic <i>E. coli hemA tonB</i> strain.</p> <p>Fur (ferric uptake regulator) has been described as a global iron-responsive regulator in &gamma-proteobacteria. If expression is forced, <i>B. quintana fur</i> is able to complement an <i>E. coli fur </i>mutant, but an endogenous promoter for the gene could not be located and native expression in <i>B. quintana</i> was not detected. Overexpression of the iron response regulator (Irr), a Fur family member, in <i>B. quintana</i> repressed <i>hut </i>locus transcription. Previous studies showed that Irr interacted with a consensus motif, the H-box, in the promoter of the <i>hbp</i> genes. A region with homology to the H-box consensus is present in the divergent promoter between <i>hutA</i> and <i>tonB</i> and in the promoter region of <i>hemS</i>.</p> <p>The fate of hemin in the bacterial cytoplasm is not well understood. HemS is a potential hemin storage/degradation enzyme. Initial characterization indicates that HemS is able to bind hemin in a 1:1 fashion with an estimated dissociation constant (Kd) of 5.9 + 1.7 &muM. Complementation analyses using <i>Corynebacterium ulcerans</i> CU712<i>hmuO</i>&delta strain have not been successful but future experiments plan to use an <i>E. coli chuS</i> strain. These studies have characterized the principal hemin uptake system of <i>B. quintana</i>, identified its transcriptional regulator, and initiated investigation of a potential heme oxygenase.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Grantor dc:publisher

University of Montana

Year

2010

Author dc:creator

• Parrow, Nermi Lee

• Bartonella
• hemin
• iron
• regulation
• Trench fever

Repository record dc:identifier

https://scholarworks.umt.edu/etd/511

OAI identifier oai:identifier

oai:scholarworks.umt.edu:etd-1530