Purification and characterisation of cell survival factor 1 (TCSF1) from Tetrahymena thermophila

Of a number of peptides isolated from the extracellular medium of Tetrahymena cultures, two with masses 9.9 and 22.4 kDa allowed low‐density cultures of this ciliate to survive and enter a proliferate phase. The smaller peptide (TCSF1) also greatly helped cultured mammalian fibroblasts to survive in medium containing very low concentrations of serum for considerably longer than controls, and to grow when full strength medium was restored. The primary sequence of the TCSF1 was determined, and synthetic TCSF1 was observed to exhibit rescuing activity comparable to that of the native peptide.