Final answer:
Pro-apoptotic BH3-only proteins exclusively contain the BH3 domain, which is integral to the process of apoptosis and is being researched for therapeutic applications in cancer treatment.
Step-by-step explanation:
Pro-apoptotic BH3-only proteins contain only the BH3 domain. These proteins are crucial in the apoptosis process, where they promote cell death. The BH3 domain is essential for these proteins to interact with other molecules in the pathway of apoptosis, enabling the cellular signalling that leads to cell death under certain conditions. Pro-apoptotic proteins, like Protein kinase N3 siRNA and BikDD plasmid DNA, are research targets in developing cancer therapies because of their role in controlling the death of cancer cells. The manipulation of these genes and the use of delivery systems like Accurins™M nanoparticles are examples of how current research is trying to harness the power of apoptosis for therapeutic benefits.