Two chemists at the University of California, San Diego have discovered the most naturally variable protein known to date in a bacterium that is a key player in the formation of dental plaque (Proceedings of the National Academy of Sciences, August 22, 2011).
The chemists believe the extreme variability of the protein they discovered in the bacterium Treponema denticola evolved to adhere to the hundreds of different kinds of other bacteria that inhabit people's mouths. They call the protein Treponema variable protein (TvpA) and estimate that it is a million to a billion times more variable than the proteins that play a primary role in vertebrate immune systems -- the only other known natural system for massive protein variation.
"In Treponema denticola, we found a protein we call TvpA that varies considerably more than proteins of the immune system, and to our knowledge this protein is the most variable natural protein described to date," said Partho Ghosh, PhD, a professor of chemistry and biochemistry at the University of California, San Diego, who headed the research effort. "We don't know what it does in this bacterium, but our hypothesis is that it enables it to adhere to the biofilm that exists in people's mouths."
Dental biofilm varies from person to person in the kinds of bacteria that adhere to the teeth to form the biofilm, Ghosh explained. Because it grows in a sequential way and because T. denticola is one of the last key players in the formation of biofilm, the bacterium has no idea what kinds of other bacteria will be present to adhere to, he added.
"We suspect that by varying TvpA, T. denticola is able to find a TvpA variant that is able to adhere to whichever bacterium is already present in the biofilm," Ghosh said.
