Mode of action of Bacillus thuringiensis Cry and Cyt toxins and their potential for insect control.
Bacillus thuringiensis Crystal (Cry) and Cytolitic (Cyt) protein families are a diverse group of proteins with activity against insects of different orders--Lepidoptera, Coleoptera, Diptera and also against other invertebrates such as nematodes. Their primary action is to lyse midgut epithelial cells by inserting into the target membrane and forming pores. Among this group of proteins, members of the 3-Domain Cry family are used worldwide for insect control, and their mode of action has been characterized in some detail. Phylogenetic analyses established that the diversity of the 3-Domain Cry family evolved by the independent evolution of the three domains and by swapping of domain III among toxins. Like other pore-forming toxins (PFT) that affect mammals, Cry toxins interact with specific receptors located on the host cell surface and are activated by host proteases following receptor binding resulting in the formation of a pre-pore oligomeric structure that is insertion competent. In contrast, Cyt toxins directly interact with membrane lipids and insert into the membrane. Recent evidence suggests that Cyt synergize or overcome resistance to mosquitocidal-Cry proteins by functioning as a Cry-membrane bound receptor. In this review we summarize recent findings on the mode of action of Cry and Cyt toxins, and compare them to the mode of action of other bacterial PFT. Also, we discuss their use in the control of agricultural insect pests and insect vectors of human diseases.
Bravo
Alejandra
A
Departamento de Microbiología Molecular, Instituto de Biotecnologia, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca, Morelos 62250, Mexico.
Gill
Sarjeet S
SS
Soberón
Mario
M
D001413:Bacillus thuringiensis / Q000737:chemistry*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000737:chemistry / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D004731:Endotoxins / Q000737:chemistry / Q000494:pharmacology*; D006460:Hemolysin Proteins / Q000737:chemistry / Q000494:pharmacology*; D019476:Insect Proteins / Q000037:antagonists & inhibitors; D007306:Insecticides / Q000737:chemistry / Q000494:pharmacology*; D010572:Pest Control, Biological; D010574:Pesticide Synergists / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D011487:Protein Conformation; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; C095416:Cry toxin receptors; D004731:Endotoxins; D006460:Hemolysin Proteins; D019476:Insect Proteins; D007306:Insecticides; D010574:Pesticide Synergists; D011956:Receptors, Cell Surface; C030956:insecticidal crystal protein, Bacillus Thuringiensis