Cloning and characterization of peptidylprolyl isomerase B in the silkworm, Bombyx mori

Abstract

Peptidylprolyl isomerases (PPIases) play essential roles in protein folding and are implicated in immune response and cell cycle control. Our previous proteomic analysis indicated that Bombyx mori PPIases may be involved in anti- Bombyx mori nucleopolyhedrovirus (BmNPV) response. To help investigate this mechanism, we cloned a B. mori PPIase gene PPIB and characterized it by bioinformatic and experimental analysis. We found that the B. mori PPIB gene contains 4 exons and its cDNA is about of
618 bp, encoding a protein of 205 amino acid residues (21474.41 Da) with an isoelectric point of 8.05. PPIB contains conserved and unique cyclophilin domain and belongs to cyclophilin superfamily. Its transcription could be detected by PCR in all the B. mori tissue samples, which is consistent with
normal PPIase expression pattern and their essential roles. It is localized in cytoplasm revealed by fluorescence microscopy. We also successfully expressed this protein in E. coli and characterized it by SDS-PAGE and Mass Spectrometry. The cloned DNA sequence was submitted to GenBank (EU583493).