Cloning and functional expression of a Boophilus microplus cathepsin L-like enzyme

A cysteine proteinase gene homologous to cathepsins L genes was isolated fr om a B. microplus cDNA library. The precursor protein deduced from the nucl eotide sequence contains 332 amino acid residues consisting of a signal seq uence (pre-region), a proregion and a mature proteinase. The DNA fragment c oding for the proenzyme was cloned and expressed using the E, coli expressi on vector pMAL-p, The recombinant protein (MBP+PROCP) once activated is abl e to hydrolyze synthetic substrates as well as:protein substrates like hemo globin, vitellin and gelatin. Its optimal enzymatic activity on both fluoro genic and protein substrates was found to occur at an acidic pH. Expression of the proteinase gene was tested by RT-PCR with tick larvae RNA. Detectio n of amplified sequences indicates that the gene is expressed at this stage of the tick life cycle and the molecule is therefore potentially a target for chemotherapy or an immunogen in a vaccine. (C) 2000 Elsevier Science Lt d. All rights reserved.