Partial characterization of an atypical family I inorganic pyrophosphatase from cattle tick Rhipicephalus (Boophilus) microplus

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• 作者：Evenilton P. Costa^a ; Eldo Campos^e ; Caroline P. de Andrade^c ; Arnoldo R. Faç ; anha^b ; Luiz Saramago^e ; Aoi Masuda^d ; Itabajara da Silva Vaz Jr.^c ; Jorge H. Fernandez^a ; Jorge Moraes^e ; Carlos Logullo^a ; ^{logullo@uenf.br}
• 关键词：Disulfide bonds ; Soluble inorganic pyrophosphatase ; Tick ; Rhipicephalus (Boophilus) microplus
• 刊名：Veterinary Parasitology
• 出版年：2012
• 出版时间：23 March 2012
• 年：2012
• 卷：184
• 期：2-4
• 页码：238-247
• 全文大小：1378 K

文摘

The present paper presents the partial characterization of a family I inorganic pyrophosphatase from the hard tick Rhipicephalus (Boophilus) microplus (BmPPase). The BmPPase gene was cloned from the tick embryo and sequenced. The deduced amino acid sequence shared high similarity with other eukaryotic PPases, on the other hand, BmPPase presented some cysteine residues non-conserved in other groups. This pyrophosphatase is inhibited by Ca²⁺, and the inhibition is antagonized by Mg²⁺, suggesting that the balance between free Ca²⁺ and free Mg²⁺ in the eggs could be involved in BmPPase activity control. We observed that the BmPPase transcripts are present in the fat body, midgut and ovary of ticks, in two developmental stages (partially and fully engorged females). However, higher transcription amounts were found in ovary from fully engorged females. BmPPase activity was considerably abolished by the thiol reagent dithionitrobenzoic acid (DTNB), suggesting that cysteine residues are exposed in its structure. Therefore, these cysteine residues play a critical role in the structural stability of BmPPase. Molecular dynamics simulation analysis indicates that BmPPase is the first Family I PPase that could promote disulfide bonds between cysteine residues 138-339 and 167-295. Finally, we believe that these cysteine residues exposed in the BmPPase structure can play an important controlling role regarding enzyme activity, which would be an interesting mechanism of redox control. The results presented here also indicate that this enzyme can be involved in embryogenesis of this arthropod, and may be useful as a target in the development of new tick control strategies.