In the heart of French Guiana, a fascinating and deadly defense mechanism has evolved within the ranks of the Neocapritermes taracua termite. These insects have developed a unique way to protect their colony – by sacrificing themselves. Older worker termites carry ‘rucksacks’ filled with a toxic liquid that they can detonate, poisoning enemies in a final act of self-destruction.
Scientists have now revealed the secrets behind these ‘suicide backpacks’ and the remarkable enzyme that powers them. Back in 2012, researchers discovered that older N. taracua workers carry blue-spotted backpacks that explode when threatened. These backpacks are filled with a blue, copper-containing enzyme called blue laccase BP76, which is stored in specialized glands within their abdomens. As they age, the termites accumulate these backpacks, ready to be deployed in an emergency.
When faced with danger, the aging workers rupture their bodies, mixing BP76 with secretions from their salivary glands. This creates a sticky liquid rich in benzoquinones, highly toxic compounds that can immobilize or kill predators.
However, the question of how BP76 could remain stable in a solid form on the termite’s back while remaining primed for an instant reaction upon rupture puzzled scientists. A new study, published in the journal Structure, has finally solved this mystery by providing the first detailed three-dimensional structure of BP76.
The research reveals that BP76 employs a variety of ingenious strategies to maintain its stability. The enzyme is tightly folded, similar to folding a piece of paper into a compact shape, which helps it resist degradation over time. Additionally, sugar molecules attach to the protein, forming a protective shield that further stabilizes it.
One of the most intriguing features of BP76 is a rare and exceptionally strong chemical bond between two amino acids, lysine and cysteine, near the enzyme’s active site. This bond, rarely found in other enzymes, plays a crucial role in maintaining BP76’s structure, especially when stored on the termite’s back. It acts like a special locking mechanism, ensuring the enzyme retains its shape and remains fully functional, ready for instant deployment when needed.
This ability to stably store and accumulate BP76 as they age is critical for colony protection. Previous studies theorized that, as termite mandibles dull over time, older workers become less effective at foraging and maintaining the nest. Their exploding rucksacks allow them to specialize in a final, deadly defense strategy, ensuring the survival of their colony.
Understanding the three-dimensional structure of BP76 helps scientists unravel the complex biological processes that allow these termites to protect themselves and their communities. This research highlights the fascinating diversity of life on Earth and the remarkable adaptations that organisms develop to survive and thrive in their environments.
