Premium
A RAS ‐encoded protein in Dictyostelium discoideum is acylated and membrane‐associated
Author(s) -
Weeks G.,
Lima A. F.,
Pawson T.
Publication year - 1987
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1987.tb01941.x
Subject(s) - dictyostelium discoideum , biology , biochemistry , cell fractionation , cytoplasm , cytosol , protease , myristic acid , subcellular localization , microbiology and biotechnology , membrane , enzyme , palmitic acid , fatty acid , gene
Summary Dictyostelium dfscoideum synthesizes a 23000 M r protein, p23 dd‐ras , closely related to the mammalian oncogene‐encoded protein p21 ras . To investigate the subcellular localization of P23 dd‐ras , conditions were optimized to reduce protein degradation following cell breakage. Subcellular fractionation of D. discoideum showed that p23 dd‐ras was associated predominantly with the membrane fraction during both vegetative growth and differentiation, in the absence of suitable protease inhibitors considerable amounts of a truncated form of p23 dd‐ras were recovered in the cytosol fraction, suggesting that intact p23 dd‐ras is attached to the membrane by a short terminal peptide sequence. Radio‐isotope labelilng of D. discoideum with myristic acid or palmitic acid in the presence of excess un‐labelled acetate resulted in radio‐isotope incorporation into a select group of proteins including p23 dd‐ras . No acyl label appeared in the truncated cytoplasmic form of p23 dd‐ras when ceil breakage was performed In the absence of suitable protease inhibitors, indicating that the acyl group is associated with the short terminal peptide that is cleaved. These data suggest that p23 dd‐ras like its mammailan counterpart, is acylated and associated with the plasma membrane. There was no evidence during a 30‐minute pulse of methionine for a cytoplasmic precursor to the membrane‐bound p23 dd‐ras suggesting that the turnover of the presumptive precursor must be much more rapid in D. discoideum than for pro‐p21 ras in mammalian cells.