Euphorbia characias latex: micromorphology of rubber particles and rubber transferase activity

We have recently characterized a natural rubber in the latex of Euphorbia characias. Following that study, we here investigated the rubber particles and rubber transferase in that Mediterranean shrub. Rubber particles, observed by scanning electron microscopy, are spherical in shape with diameter ranging from 0.02 to 1.2 μm. Washed rubber particles exhibit rubber transferase activity with a rate of radiolabeled [(14)C]IPP incorporation of 4.5 pmol min(-1)mg(-1). Denaturing electrophoresis profile of washed rubber particles reveals a single protein band of 37 kDa that is recognized in western blot analysis by antibodies raised against the synthetic peptide whose sequence, DVVIRTSGETRLSNF, is included in one of the five regions conserved among cis-prenyl chain elongation enzymes. The cDNA nucleotide sequence of E. characias rubber transferase (GenBank JX564541) and the deduced amino acid sequence appear to be highly homologous to the sequence of several plant cis-prenyltransferases.