Structure-function studies of human ciliary neurotrophic factor

Ciliary neurotrophic factor (CNTF) is a polypeptide that promotes the survival and/or differentiation of a number of neural cell types. Here we present a structural and functional analysis of the human CNTF molecule. Variant proteins were synthesized byEscherichia coli trnsformmed with mutant cDNA constructs, and purified by SDS-polyacrylamide gel electrophoresis and reverse phase high pressure liquid chromatography. Most variant CNTF proteins lacked neurotrophic activity, but two N-and C-terminal deletions (2–14 and 173–200, respectively) actually displayed a several-fold increase in specific activity. Loss of biological activity was accompanied by changes in the alphahelical nature of CNTF as measured by circular dichroism. These data strengthen the proposed similarity between CNTF and the family of hematopoietic cytokines.