JBC, Vol. 250, Issue 17, 6806-6816, Sep, 1975
Studies of the formation of peptide cross-links in the cell wall peptidoglycan of Streptococcus faecalis
P. Dezelee and G. D. Shockman
A method was developed to label specifically the glycan chains of the cell
wall peptidoglycan of Streptococcus faecalis ATCC 9790 with [14C]acetate.
The formation of peptide cross-links (a) during exponential growth, (b)
after valine starvation and wall thickening, and (c) during regrowth after
2 hours of valine starvation, was studied using continuous, pulse and
pulse-chase labeling of the peptidoglycan with both [14C]acetate and
[3H]lysine. After labeling, walls were isolated, digested with the
muramidase of Chalaropsis B, and the "free" peptidoglycan fragments (75 to
90% of the total peptidoglycan) were then fractionated on columns of
Sephadex G-50, G-50, and G-25 in series into disaccharide-peptide monomer
and peptide cross-linked bisdisaccharide-peptide dimer,
trisdisaccharide-peptide trimer, and higher oligomer fractions.
Peptidoglycan made during valine starvation and wall thickening was found
to be slightly more cross-linked than peptidoglycan made during exponential
growth. Pulse and pulse-chase experiments indicated that peptide
cross-linking continued for an unexpectedly long time after incorporation
of precursors into insoluble peptidoglycan.
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