**Interactions of Destruxin A with Silkworms' Arginine tRNA Synthetase and Lamin-C Proteins**

#### **Jingjing Wang, Qunfang Weng, Fei Yin and Qiongbo Hu \***

Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province; College of Agriculture, South China Agricultural University, Guangzhou 510642, China; wangjingjing@stu.scau.edu.cn (J.W.); wengweng@scau.edu.cn (Q.W.); yfei2020@stu.scau.edu.cn (F.Y.)

**\*** Correspondence: hqbscau@scau.edu.cn

Received: 30 December 2019; Accepted: 21 February 2020; Published: 22 February 2020

**Abstract:** Destruxin A (DA), a cyclodepsipeptidic mycotoxin produced by entomopathogenic fungus *Metarhizium anisopliae*, has good insecticidal activity and potential to be a new pesticide. However, the mechanism of action is still obscure. Our previous experiments showed that DA was involved in regulation of transcription and protein synthesis and suggested that silkworms' arginine tRNA synthetase (BmArgRS), Lamin-C Proteins (BmLamin-C) and ATP-dependent RNA helicase PRP1 (BmPRP1) were candidates of DA-binding proteins. In this study, we employed bio-layer interferometry (BLI), circular dichroism (CD), cellular thermal shift assay (CETSA), and other technologies to verify the interaction of DA with above three proteins in vitro and in vivo. The results of BLI indicated that BmArgRS and BmLamin-C were binding-protein of DA with KD value 5.53 × 10−<sup>5</sup> and 8.64 × 10−<sup>5</sup> M, but not BmPRP1. These interactions were also verified by CD and CETSA tests. In addition, docking model and mutants assay in vitro showed that BmArgRS interacts with DA at the pocket including Lys228, His231, Asp434 and Gln437 in its enzyme active catalysis region, while BmLamin-C binds to DA at His524 and Lys528 in the tail domain. This study might provide new insight and evidence in illustrating molecular mechanism of DA in breaking insect.

**Keywords:** Destruxins; *Bombyx mori*; BmArgRS; BmLamin-C; RNA helicase; binding protein

**Key Contribution:** BmArgRS and BmLamin-C are binding protein of Destruxin A in silkworm Bm12 cells. BmArgRS interacts with DA in its enzyme active catalysis region at Lys228, His231, Asp434 and Gln437. BmLamin-C binds to DA in its lamin tail domain at His524 and Lys528.
