Perforin: structure and function.

Perforin is a cytolytic mediator produced by killer lymphocytes, and is stored in and released by cytoplasmic granules. The protein is partially homologous to the terminal components of the membrane attack complex of complement and produces pores of up to 20 nm in diameter on target membranes. Its genomic and protein structures have recently been unraveled, and its function elucidated through the availability of genetically engineered, perforin-deficient mice. Here Chau-Ching Liu, Craig M. Walsh and John Ding-E Young briefly outline certain biochemical and molecular features of perforin, and discuss the still-evolving issues concerning the relevance of perforin and Fas in cell killing.