The present invention provides a method to obtain DNA constructs that encode 3-domain Cry toxins (also called Cry toxins, Bt toxins, or β-endotoxins) lacking helix α-1. These DNA constructs have been modified to encode proteins that kill insects that are resistant to the corresponding unmodified Cry toxins. The DNA constructs encoding the Modified 3-Domain Cry Toxins and the encoded Modified 3-Domain Cry Toxins are provided together with the molecular vectors and the host cell comprising said constructs and the recombinant methods to produce the Modified 3-Domain Cry Toxins. Additionally, compositions comprising the Modified 3-Domain Cry Toxins are disclosed. The resistance of the insects to unmodified Cry toxins is due to reduced toxin binding to the insects' midgut receptors. The invention further provides methods to overcome resistance in crop pests.