CHARACTERIZATION OF A NUCLEOTIDE-SENSITIVE HIGH-MOLECULAR-WEIGHT MICROTUBULE-ASSOCIATED PROTEIN IN THE OVARY OF A HEMIPTERAN INSECT

We have identified a 260 kD polypeptide as being the major microtubule-associated protein (MAP) in the ovaries of the hemipteran insect, Oncopeltus fasciatus. The 260 kD insect ovarian MAP resembles certain mammalian brain MAPs by remaining soluble after boiling and promoting the assembly of tubulin into microtubles. It differs from most MAPs by exhibiting nucleotide-sensitivity, being removed from microtubules by both ATP and GTP. Antibodies specific for the 260 kD MAP allowed its immunofluorescent localization to the massive microtubule aggregates forming the translocation systems which in hemipterans link the developing oocytes with anteriorly positioned nutritive cells. Such antibodies, in conjunction with electrophoretic methods, also demonstrated the 260 kD MAP to be species- and, to an extent at least, tissue-specific. The Oncopeltus 260 kD MAP was not present in the ovaries of either Notonecta or Corixa, hemipterans which have similar microtubule systems to Oncopeltus but MAPs of slightly different molecular weight. The 260 kD MAP from the ovaries of Oncopeltus was not present in neuronal ganglia of the same species. The significance of the species- and tissue-specificity of the 260 kD MAP, as well as its nucleotide-sensitivity, are speculated upon and discussed.