Serotype Association and Regulation of the Hyaluronate Lyase Gene of <i>Streptococcus pyogenes</i>

<p><em>S. pyogenes</em> expresses many virulence factors, controlled by a complex regulatory network. These include hyaluronate lyase, an enzyme that degrades hyaluronic acid, a major component of the human extracellular matrix. Paradoxically, hyaluronic acid is also the sole component of the bacterium's capsule, a primary defense against the host immune response. The <em>hyl</em>A gene, which encodes the enzyme, has been shown to take three structural forms: a full-length gene, one containing a 3' deletion and a gene that produces a prematurely truncated protein. This work was intended to show that the structure of <em>hyl</em>A is associated with serotype, and therefore, disease pattern of <em>S. pyogenes.</em></p> <p>The structure of <em>hyl</em>A was determined to have two regions where changes that influence amino acids, and therefore protein structure, result in a loss of enzymatic activity. The 3' region contains the deletion and the premature stop codon, and an area of the 5' region contains a one-amino acid change that leads to a loss of activity. Site-directed mutagenesis of the amino acid in the 5' region resulted in a restoration of activity in a truncated strain but not in a deleted strain, suggesting a relationship between the 3' and 5' domains.</p> <p>Epidemiological studies of a number of strains showed that serotypes containing the full-length <em>hyl</em>A gene produce an active enzyme, while other serotypes have one of the other two gene structures and do not produce an active enzyme. Enzyme-producing serotypes of <em>S. pyogenes </em>correlate with non-invasive infection, whereas those serotypes causing more invasive and life-threatening infections tend to be enzyme-negative.</p> <p>Mutagenesis of proteins associated with other virulence factors in <em>S. pyogenes</em> gene failed to identify the regulator of hylA expression. The <em>mga</em> gene, the <em>cov</em>R gene and other two-component response regulators were knocked out, but none were shown to affect <em>hyl</em>A expression. Further investigations will explore other regulators controlling virulence factors and metabolic processes.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Year dc:date.available

2007

Author dc:creator

• Stokes, Martha

Contributors dc:contributor

• Waynes Hynes
• Christopher Osgood
• Fred Dobbs
• Alex Greenwood

• Hyaluronate lyase
• Serotype
• Streptococcus pyogenes
• Virulence
• Microbiology
• Molecular Biology

Identifier

9780549218272

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:biomedicalsciences_etds-1080