A HEME-BINDING PROTEIN FROM HEMOLYMPH AND OOCYTES OF THE BLOODSUCKINGINSECT, RHODNIUS-PROLIXUS - ISOLATION AND CHARACTERIZATION

A heme-binding protein has been isolated and characterized from both t he hemolymph and oocytes of the blood sucking insect, Rhodnius prolixu s, The protein from both sources is identical in most aspects studied. The Rhodnius heme binding protein (RHBP) is com posed of a single 15- kDa polypeptide chain coiled in a highly alpha-helical structure which binds non-covalently one heme/polypeptide chain, This RHBP is not pro duced by limited degradation of hemoglobin from the vertebrate host, s ince specific polyclonal antibodies against it do not cross-react with rabbit hemoglobin, and since it differs from hemoglobin in having a d istinct amino-acid composition and NH2-terminal sequence, The spectrum of the dithionite-reduced protein has peaks at 426, 530, and 559 nm a nd resembles that of a b-type cytochrome. RHBP from hemolymph is not s aturated with heme and promptly binds heme added to the solution, The oocyte protein, on the other hand, is fully saturated and is not capab le of binding additional heme.