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Dennis Arvidson, Ph.D.

Research

My major research interest is the structure and function of proteins involved in bacterial pathogenesis. Current work is focused on the preparation of crystals of bacterial virulence factors suitable for x-ray diffraction. A number of investigations are underway.

Gly1Orf1 is a secreted protein that affects the toxicity of Neisseria gonorrhoeae to human fallopian tubes in organ culture. This protein is produced only in pathogenic Neisseria species. In collaboration with Dr. Cindy Arvidson (MSU), hexagonal (space group P63) data quality crystals of the 15 kDa protein have been prepared. A synthetic mother liquor compatible with cryocrystallography has been developed. I have collected a native data set to 2.1Å resolution, and a heavy atom derivative data set. More recently, MAD data sets of a selenomethionine derivative were collected.

Crystallization studies are in progress, in collaboration with Dr. Kwong-Kwok Wong (Pacific Northwest National Laboratories), of a Salmonella typhimurium cytotoxin. This >300 kDa protein is an RTX-like toxin that forms pores in the cell membrane. We are currently working with an 88 kDa domain of the protein with 6 RTX-toxin motifs (a nanopeptide sequence) that has been purified and shown to be cytotoxic.

Drs. Fred Heffron and Sunghee Chai (Oregon Health Sciences University) have provided plasmid constructs for virulence factors from Salmonella typhimurium. A protein currently named IMS75 was discovered in a screen for genetic loci that, when disrupted, impair macrophage survival. This protein was also found in a subsequent screen for proteins that are localized to the host cytoplasm. IMS75 thus appears to be transported from the phagolysosome to the host cytoplasm where it may interact to allow survival of the bacteria within the phagolysosome.