Pacheco Sabino, Gómez Isabel, Peláez-Aguilar Angel E, Verduzco-Rosas Luis A, García-Suárez Rosalina, do Nascimento Nathaly A, Rivera-Nájera Lucero Y, Cantón Pablo Emiliano, Soberón Mario, Bravo Alejandra
Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico.
Front Insect Sci. 2023 Apr 26;3:1188891. doi: 10.3389/finsc.2023.1188891. eCollection 2023.
Different (Bt) strains produce a broad variety of pore-forming toxins (PFTs) that show toxicity against insects and other invertebrates. Some of these insecticidal PFT proteins have been used successfully worldwide to control diverse insect crop pests. There are several studies focused on describing the mechanism of action of these toxins that have helped to improve their performance and to cope with the resistance evolved by different insects against some of these proteins. However, crucial information that is still missing is the structure of pores formed by some of these PFTs, such as the three-domain crystal (Cry) proteins, which are the most commercially used Bt toxins in the biological control of insect pests. In recent years, progress has been made on the identification of the structural changes that certain Bt insecticidal PFT proteins undergo upon membrane insertion. In this review, we describe the models that have been proposed for the membrane insertion of Cry toxins. We also review the recently published structures of the vegetative insecticidal proteins (Vips; e.g. Vip3) and the insecticidal toxin complex (Tc) in the membrane-inserted state. Although different Bt PFTs show different primary sequences, there are some similarities in the three-dimensional structures of Vips and Cry proteins. In addition, all PFTs described here must undergo major structural rearrangements to pass from a soluble form to a membrane-inserted state. It is proposed that, despite their structural differences, all PFTs undergo major structural rearrangements producing an extended α-helix, which plays a fundamental role in perforating their target membrane, resulting in the formation of the membrane pore required for their insecticidal activity.
不同的苏云金芽孢杆菌（Bt）菌株产生多种成孔毒素（PFTs），这些毒素对昆虫和其他无脊椎动物具有毒性。其中一些杀虫PFT蛋白已在全球范围内成功用于控制多种农作物害虫。有几项研究专注于描述这些毒素的作用机制，这有助于提高它们的性能，并应对不同昆虫对其中一些蛋白产生的抗性。然而，仍然缺少的关键信息是某些PFTs形成的孔的结构，例如三结构域晶体（Cry）蛋白，它们是生物防治害虫中最常用的Bt毒素。近年来，在确定某些Bt杀虫PFT蛋白在膜插入时所经历的结构变化方面取得了进展。在这篇综述中，我们描述了针对Cry毒素膜插入提出的模型。我们还综述了最近发表的营养期杀虫蛋白（Vips；例如Vip3）和处于膜插入状态的杀虫毒素复合物（Tc）的结构。尽管不同的Bt PFTs具有不同的一级序列，但Vips和Cry蛋白的三维结构存在一些相似之处。此外，本文描述的所有PFTs都必须经历重大的结构重排，才能从可溶形式转变为膜插入状态。有人提出，尽管它们的结构不同，但所有PFTs都会经历重大的结构重排，产生一个延伸的α-螺旋，这在穿透其靶膜中起着基本作用，导致形成其杀虫活性所需的膜孔。
