Characterization of proteinases from the midgut of Rhipicephalus (Boophilus) microplus involved in the generation of antimicrobial peptides

BACKGROUND: Hemoglobin is a rich source of biologically active peptides, some of which are potent antimicrobials (hemocidins). A few hemocidins have been purified from the midgut contents of ticks. Nonetheless, how antimicrobials are generated in the tick midgut and their role in immunity is still p...

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Bibliographic Details
Published in:Parasites & vectors 2010-07, Vol.3 (1), p.63-63, Article 63
Main Authors: Cruz, Carlos E, Fogaça, Andréa C, Nakayasu, Ernesto S, Angeli, Cláudia B, Belmonte, Rodrigo, Almeida, Igor C, Miranda, Antônio, Miranda, Maria Terêsa M, Tanaka, Aparecida S, Braz, Glória R, Craik, Charles S, Schneider, Eric, Caffrey, Conor R, Daffre, Sirlei
Format: Article
Language:English
Subjects:
amino acids
antimicrobial agents
Antimicrobial peptides
Aspartic proteinases
Boophilus microplus
cathepsin L
cattle
chromatography
flora
hemoglobin
immunity
Ixodidae
midgut
pathogens
peptide libraries
Physiological aspects
polymerase chain reaction
Rhipicephalus
tick control
Ticks
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Summary:BACKGROUND: Hemoglobin is a rich source of biologically active peptides, some of which are potent antimicrobials (hemocidins). A few hemocidins have been purified from the midgut contents of ticks. Nonetheless, how antimicrobials are generated in the tick midgut and their role in immunity is still poorly understood. Here we report, for the first time, the contribution of two midgut proteinases to the generation of hemocidins. RESULTS: An aspartic proteinase, designated BmAP, was isolated from the midgut of Rhipicephalus (Boophilus) microplus using three chromatographic steps. Reverse transcription-quantitative polymerase chain reaction revealed that BmAP is restricted to the midgut. The other enzyme is a previously characterized midgut cathepsin L-like cysteine proteinase designated BmCL1. Substrate specificities of native BmAP and recombinant BmCL1 were mapped using a synthetic combinatorial peptide library and bovine hemoglobin. BmCL1 preferred substrates containing non-polar residues at P2 subsite and polar residues at P1, whereas BmAP hydrolysed substrates containing non-polar amino acids at P1 and P1'. CONCLUSIONS: BmAP and BmCL1 generate hemocidins from hemoglobin alpha and beta chains in vitro. We postulate that hemocidins may be important for the control of tick pathogens and midgut flora.
ISSN:1756-3305
1756-3305
DOI:10.1186/1756-3305-3-63