Preparation, application and biological characterization of interleukin-1 beta mutant protein biotinylated at a single site.

Selective biotinylation of human interleukin-1 beta was achieved by reaction of an interleukin-1 beta mutant protein containing a surface-accessible cysteine with maleimido-biotin. A defined interleukin-1 beta derivative biotinylated at a single site was obtained. This compound retained full affinity for both the interleukin-1 receptor and streptavidin or avidin; however, its biological activity was significantly reduced in proliferative assays. Biotinylated interleukin-1 beta mutant protein bound to fluorescein-labelled avidin was used in flow cytometric analysis of interleukin-1 receptors. Internalization of the complex between biotinylated interleukin-1 beta mutant protein and streptavidin in a murine thymoma cell line was demonstrated.