Molecular syringe ferries proteins into human cells

Researchers have repurposed a bacterium’s molecular ‘syringe’ to deliver proteins, such as the genome-editing Cas9 or a cancer-killing toxin, into human cells or the brains of mice. The bacterium Photorhabdus asymbiotica’s injection system usually works only on insect cells. The team modified the structure of the system so that it would recognize other species’ cells and accept payloads including the Cas9 protein, which is five times larger than the syringe’s usual cargo. The method could be a way to administer protein-based drugs and address one of gene editing’s major bottlenecks: delivering the CRISPR–Cas9 system to where it’s needed.