神马福利影片

 

Researchers at the University of Warwick have discovered how a protein  from a bacterium acts  like a cunningly designed poison pill box that could now be used as a basis of a new range of natural insecticides. It had been known that nematode worms  can infect and kill insect pests with the help of a bacterium which they harbour inside their intestine. 

The bacterium uses a protein (XptA1)  a toxin  which  helps the nematode to kill and feed on the dead body of the insect. The toxin not only kills the target insect but prevents other predators from eating the body giving free reign to the nematode worms to consume it, multiply and move on. However, until now, researchers had little idea of the make up of XptA1 and thus how it worked.  The research team, based at the University of Warwick鈥檚 horticultural research arm Warwick HRI, have now been able to reveal  the shape of the protein XptA1 and discovered a number of properties that make it a particularly efficient natural  insecticide and possible alternative to some commercial insecticides that are facing increased resistance in the insect populations they target. 

The researchers at Warwick HRI, together with a team of colleagues  with expertise in the Structural Biology group in Biological Sciences and in Chemistry at The 神马福利影片, as well as Coventry and Nottingham Universities, found that the protein was formed from four sub units in the shape of a hollow cage or box which is configured to bind  well to part of a caterpillar鈥檚 gut called 鈥淏rush Border Membrane Vesicles鈥�  (BBMV).

The XptA1 protein seemed to specifically target the BBMV of caterpillars Pieris Brassicae 鈥� (The cabbage white butterfly caterpillar which are pests for many growers).  The hollow box structure appears to be a key element of the protein鈥檚 design. The hollow shape allows the protein to act as a receptacle for two other proteins (in the case of XptA1 these are  XptB1 and XptC1). This forms a poison 鈥渃omplex鈥� which makes the XptA1 300 times more toxic to the caterpillars than it would be by itself. As well as helping collect together the three proteins and attach them to the insect鈥檚 gut the researchers think that the box shape of the XptA1 protein possibly also helps protect the poison complex from the acid attack they would face from the high pH values in the insect gut. The researchers also discovered that, while XptA1 was highly selective in that it bound to the cabbage white butterfly  caterpillar, there were variants of this family of toxic proteins (such as XptA2)  that targeted other insects. 

Dr Sarah Lee from the University of Warwick said: 鈥淭his research gives us crucial new insights into a family of naturally occurring proteins that are toxic to a number of insect pests. They offer an alternative to current commercial protein based insect toxins have been in use for 40 years and are now starting to meet some resistance. This potential new family of protein based insecticides would overcome such resistance as they operate in an entirely different way鈥� 

The research has been published in the 9th March issue of The Journal of Molecular Biology Volume 366 Issue 5 pages 1558 鈥� 1568. The paper is titled 鈥淪tructural Characterisation of the Insecticidal Toxin XptA1, Reveals a 1.15 MDa Tetramer with a Cage-like Structure鈥�

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 For further information please contact:     

Dr Sarah Lee, Warwick HRI, University of Warwick
Tel 02476575144 Email s.c.lee@warwick.ac.uk 

Peter Dunn, Press and Media Relations Manager, Communications Office,
University of Warwick, Tel: 024 76 523708 or 07767 655860
email: p.j.dunn@warwick.ac.uk 

PR15  PJD  12th March  2007