New discovery on dental plaque bacterium

Experts have discovered the most naturally variable protein known to date in a bacterium that’s a key player in the formation of dental plaque.

The chemists, from UC San Diego, US w, announced their discovery in this week’s online edition of the journal Proceedings of the National Academy of Sciences.

They say they 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 they discovered ‘Treponema variable protein’ – or TvpA – and estimate 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.

Partho Ghosh, a professor of chemistry and biochemistry at UC San Diego who headed the research effort, says: ‘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.

‘We don’t know what it does in this bacterium, but our hypothesis is that it enables it to adhere to the biofilm, commonly known as dental plaque, that exists in people’s mouths.’

Professor Ghosh explained that dental plaque varies from person-to-person in the kinds of bacteria that adhere to the teeth to form this biofilm.

Because plaque grows in a sequential way and because T. denticola is one of the last key players in the formation of plaque, Ghosh said the bacterium has no idea what kinds of other bacteria will be present to adhere to.

‘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.

Ghosh and Johanne Le Coq, a postdoctoral fellow in his laboratory now working at the Spanish National Cancer Centre in Madrid, determined the structure of their newly discovered protein and its extreme variability using a powerful X-ray ‘microscope’ at the Advanced Photon Source at the Argonne National Laboratory near Chicago.

Their research project was supported by the US Department of Energy, National Cancer Institute, National Institute of General Medical Science and National Institute of Allergy and Infectious Diseases. 

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