STIMULATION OF TRYPANOSOMA-CRUZI ADENYLYL-CYCLASE BY AN ALPHA(D)-GLOBIN FRAGMENT FROM TRIATOMA-HINDGUT - EFFECT ON DIFFERENTIATION OF EPIMASTIGOTE TO TRYPOMASTIGOTE FORMS

A peptide from hindguts of the Triatoma hematophagous Chagas insect ve ctor activates adenylyl cyclase activity in Trypanosoma cruzi epimasti gote membranes and stimulates the in vitro differentiation of epimasti gotes to metacyclic trypomastigotes. Hindguts were obtained from insec ts fed 2 days earlier with chicken blood. Purification was performed b y gel filtration and HPLC on C18 and C4 columns. SDS/PAGE of the purif ied peptide showed a single band of about 10 kDa. The following sequen ce was determined for the 20 amino-terminal residues of this peptide: s-Leu-Ile-Gln-Gln-Ala-Trp-Glu-Lys-Ala-Ala-Ser-His. This sequence is id entical to the amino terminus of chicken alpha(D)-globin. On a Western blot, the peptide immunoreacted with a polyclonal antibody against ch icken globin D. A synthetic peptide corresponding to residues 1-40 of the alpha(D)-globin amino terminus also stimulated adenylyl cyclase ac tivity and promoted differentiation. This I-125-labeled synthetic pept ide bound specifically to T. cruzi epimastigote cells. Activation of e pimastigote adenylyl cyclase by the hemoglobin-derived peptide may pla y an important role in T. cruzi differentiation and consequently in th e transmission of Chagas disease.