Antimicrobial activity of a bovine hemoglobin fragment in the tick Boophilus microplus

Antifungal and antibacterial activities were detected in the hemolymph and gut contents of the cattle tick, Boophilus microplus. A peptide with antiba cterial activity from the tick gut contents was purified to homogeneity by reversed-phase chromatography. The molecular mass of the purified peptide w as 3,205.7 Da, measured by matrix-assisted laser desorption/ionization mass spectrometry. The amino acid sequence was obtained by Edman degradation an d showed that the peptide was identical to a fragment of the bovine cu-hemo globin. A synthetic peptide based on the sequence obtained showed character ization data identical to those of the isolated material, confirming its st ructure. The synthetic peptide was active in micromolar concentrations agai nst Gram-positive bacteria and fungi. These data led us to conclude that th e antibacterial activity detected in tick gut contents is the result of enz ymatic processing of a host protein, hemoglobin. This activity may be used by ticks as a defense against microorganisms.