WASHINGTON - A TINY protein seems to be to blame for destroying brain cells in patients suffering from the devastating, incurable Huntington's disease, a study said on Thursday.

Another faulty protein, called 'huntingtin,' has long been known to be the cause of Hungtington's Disease.

But now researchers at Johns Hopkins University in Baltimore say they have finally worked out why the huntingtin protein accumulates in cells everywhere, but only kills cells in the part of the brain that controls movement.

They said in the study published on Thursday in Science magazine that the tiny protein, Rhes, only found in the brain cells which cause movement seemed to be to blame.

'It's always been a mystery why, if the protein made by the HD gene is seen in all cells of the body, only the brain, and only a particular part of the brain, the corpus striatum, deteriorates,' said Solomon Snyder, professor of neuroscience at Johns Hopkins.

'By finding the basic culprit, the potential is there to develop drugs that target it and either prevent symptoms or slow them down.' Carrying out tests on sufferers and on the brain cells of mice induced with the disease, the team found that the Rhes protein attached itself more strongly to the mutant huntingtin protein than proteins in other cells.

And within 48 hours the affected brain cells had died.

Huntington's is caused by a genetic defect, passed down from parent to child, that produces a mutant version of the huntingtin protein that gathers in all cells of the body.

But it is its effects on the brain that causes patients to suffer irreversible loss of the ability to their control movements, eventual mental impairment, behavioural problems and death.

'Now that we've uncovered the role of Rhes, it's possible that drugs can be designed that specifically target Rhes to treat or even prevent the disease,' said Prof Snyder. -- AFP