Patatin, a major soluble protein of the potato (Solanum tuberosum L.) tuber is synthesized as a larger precursor.

Antibodies were raised against the highly purified glycoprotein patatin. They were used to characterize the product synthesized in a wheatgerm cell-free translation system, programmed with polyadenylated RNA from potato tubers. Sodium dodecylsulfate-polyacrylamide gel electrophoresis revealed that the immunoprecipitated protein had a molecular mass of 43 kDa compared to 40 for the authentic patatin. It is assumed that patatin is synthesized in vivo as a larger precursor which is processed to the mature protein by cleavage of a signal peptide. Our results are in agreement with sequence-analysis data of patatin complementary DNA which indicate a signal peptide of about 23 amino acids (Mignery et al., 1984; Nucleic Acids Res. 12, 7987-8000).