Expression and Functional Analysis of BmFKBP45 in the Silkworm, Bombyx mori

The expression and function of the Drosophila DmFKBP39 homolog in the Silkworm, BmFKBP45, were analyzed in this study. By comparing the amino acid sequences of DmFKBP39 and BmFKBP45, it is found that both of them contained an acidic amino acid region, a basic amino acid region, a nuclear localization signal and a FKBP domain. Alignment for the DNA binding domain of HMG2 with the second basic region of BmFKBP45 shows a similarity of 21%, suggesting that BmFKBP45 may be capable of DNA binding through the second basic amino acid region. However, EMSA experiment showed that BmFKBP45 did not bind to DmJHRE1. The RT-PCR and western blot results indicated that BmFKBP45 expressed at different developmental stages in the silkworm wing disc and its expression decreased gradually during the pupal period. The hormone treatment assays demonstrated that the expression of BmFKBP45 was not changed by either ecdysone (20E) or juvenile hormone (JH). The pull-down, far-western blot and Co-IP experiments indicated an interaction between BmFKBP45 and Bm6G1, which provides a new perspective for further exploring the function of BmFKBP45.