PubMed Journals: J Biol Chem
Source: PMID: 8440735
⇦ ⇨ J Biol Chem. 1993 Feb 25;268(6):4530-3.
Identification of 40 S ribosomal protein
S6 phosphorylation sites in Swiss mouse
3T3 fibroblasts stimulated with serum.
Bandi HR(1), Ferrari S, Krieg J, Meyer HE,
(1) Friedrich Miescher Institute, Basel,
All of the phosphorylation sites in 40 S
ribosomal protein S6 derived from serum-stimulated
Swiss mouse 3T3 cells are found within a
small cyanogen bromide (CNBr) peptide derived
from the carboxyl terminus, Lys218-Lys249.
Further cleavage of the CNBr peptide or
the intact protein with endoproteinase Lys-C
(endo Lys-C) generated a single phosphorylated
peptide, implying that all the sites of
phosphorylation resided either between Arg231
and Lys243 or between Arg231 and Lys249
if cleavage at Lys243 was blocked by phosphorylation
at a nearby residue. To discern between
these possibilities and to identify the
phosphorylation sites, the protein was purified
from serum-stimulated cells and cleaved
with endo Lys-C, and the single endo Lys-C
phosphorylated peptide was isolated and
sequenced following conversion of all the
phosphorylated serines to S-ethylcysteine.
The results show that the phosphorylated
peptide extends from Arg231 to Lys249 and
that the sites of phosphorylation in vivo
are Ser235, Ser240, Ser244, and Ser247.
PMID: 8440735 [Indexed for MEDLINE]