1203. Rubrerythrin from Trichomonas vaginalis -  structural insights into the mechanism of a potential parasitic virulence factor
Session: Oral Abstract Session: Biomarkers of Infectious Diseases
Saturday, October 5, 2013: 9:06 AM
Room: The Moscone Center: 300
Background:

Trichomoniasis is a common STD with an estimated prevalence of 4 million infections in the United States. Most cases are asymptomatic, but can increase susceptibility to other more damaging STDs, including HIV. The organism that causes trichomoniasis, Trichomonas vaginalis, is essentially anaerobic and contains proteins such as peroxidases that help detoxify reactive oxygen species that it encounters in its environment.

A unique non-haem peroxidase called rubrerythrin is found in this organism. It is homologous to bacterial proteins that function as peroxidases and could represent a target for therapeutic intervention given the importance of an anaerobic environment for the organism's survival. We have been studying two main forms , the wild-type rubrerythrin which is reddish in color and a mutant protein, T48A, which is purple.

Methods:

In order to more fully understand the function of this protein, we have determined its three dimensional structure using protein crystallography. The Rbr gene from T. vaginalis was cloned and expressed in E. coli and purified using liquid chromatography. Crystallization was carried out using vapor diffusion methods. Following optimization, crystals were surveyed at the Australian Synchrotron in Melbourne. Data sets were collected and solved using CCP4i and analyzed with standard crystallographic software. Kinetic analysis was carried out using standard methodology.

Results:

The Rbr structure is a dimer of four helix bundles each containing two metal centers in a geometry and fold very similar to their bacterial orthologs. Kinetic studies indicate that it can function as an efficient peroxidase, but only if all sites are occupied by iron. In our structure the metals sites turned out to contain a mixture of both iron and zinc, but this incorporation did not affect the fold. The key to the purple color of the T48A mutant rubrerythrin appears to involve the serendipitous formation of a charge-transfer complex involving the diiron site and a tyrosine which is facilitated by this mutation.

Conclusion:

This structure represents the first structure of a eukaryotic non-haem iron peroxidase which is a potentially important virulence factor in T. vaginalis and will serve as a basis for further work to characterize its function within the organism.

Helen Opel-Reading1, Sylvia Luckner, Ph. D.1, Ruth Schaller2, Donald Kurtz, Ph.D2 and Kurt Krause, MD, PhD, FIDSA1, (1)Biochemistry, University of Otago, Dunedin, New Zealand, (2)Chemistry, University of Texas At San Antonio, San Antonio, TX

Disclosures:

H. Opel-Reading, None

S. Luckner, None

R. Schaller, None

D. Kurtz, None

K. Krause, None

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