PIXE-electrophoresis shows starving collembolan reallocates protein-bound metals
One of multiple functions of metalloproteins is to provide detoxification to excess metal levels in organisms. Here we address the induction and persistence of a range of low to high molecular weight copper- and zinc binding proteins in the collembolan species Tetrodontophora bielanensis exposed to copper- and zinc-enriched food, followed by a period of recovery from metal exposure, in absence and presence of food. After 10 days of feeding copper and zinc contaminated yeast, specimens were either moved to ample of leaf litter material from their woodland stand of origin or starved (no food offered). The molecular weight distribution of metal binding proteins was determined by native polyacryl gel electrophoresis. One gel was stained with Comassie brilliant blue and a duplicate gel dried and scanned for the amount of copper and zinc by particle-induced X-ray emission. Specimens exposed to copper and recovered from it with ample of food had copper bound to two groups of rather low molecular weight proteins (40–50 kDa) and two of intermediate size (70–80 kDa). Most zinc in specimens from the woodland stand was bound to two large proteins of about 104 and 106 kDa. The same proteins were holding some zinc in metal-exposed specimens, but most zinc was found in proteins <40 kDa in size. Specimens recovered from metal exposure in presence of ample of food had the same distribution pattern of zinc binding proteins, whereas starved specimens had zinc as well as copper mainly bound to two proteins of 8 and 10 kDa in size. Thus, the induction and distribution of copper- and zinc-binding proteins depend on exposure conditions, and the presence of low molecular weight binding proteins, characteristic of metallothioneins, was mainly limited to starving conditions.
KeywordsCollembola Metal Protein PIXE Electrophoresis Starvation Metallothionein Metalloprotein PAGE
We are grateful to Heike Reise, Senckenberg Museum for Natural Science Görlitz, for providing T. bielanensis. The study was financed by the European Environmental Research Organization (EERO), The German Academic Exchange Service (DAAD, Bonn), and the Swedish Institute (SI, Stockholm). Thanks are also due to Sten Rundgren, Lund University, and to Kåseberga-Fisk AB, Löderup, for motivational support.
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Conflict of interest
The authors declare that they have no competing interests.
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