Novel serine phosphorylation occurs in the fibroblast form of pp60c-src from Y79 retinoblastoma cells.
Two-dimensional tryptic peptide analysis showed that pp60c-src from the human retinoblastoma cell line Y79 gave a unique phosphopeptide, which was not found in human fibroblast RT59. There was no significant difference in the extent of phosphorylation of other peptides between the two cell lines. Only phosphoserine was detected in this phosphopeptide. Both the fibroblast form and the neuronal form of pp60c-src from Y79 cells had this unique peptide phosphorylated to the same extent. The phosphorylation site was inferred to be serine 97 by comparing the tryptic map and the arginyl-endopeptidase map. The specific protein kinase activity of pp60c-src from Y79 cells was nearly equal to that of RT59 pp60c-src. This unique serine phosphorylation in the fibroblast form was discussed in relation to the oncogenic change of Y79 cells.
Kato
G
G
Department of Biochemistry, Yamanashi Medical College, Japan.
Wakabayashi
K
K
D002460:Cell Line; D015180:Electrophoresis, Gel, Two-Dimensional; D010450:Endopeptidases; D005134:Eye Neoplasms; D006801:Humans; D010446:Peptide Fragments / Q000302:isolation & purification; D010449:Peptide Mapping; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000302:isolation & purification / Q000378:metabolism*; D012175:Retinoblastoma
D010446:Peptide Fragments; D010710:Phosphates; D010768:Phosphoserine; D016392:Proto-Oncogene Proteins pp60(c-src); D010450:Endopeptidases