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Heterogeneity of Newly Inserted and Preexisting Murein in the Sacculus of Escherichia coli
Miguel Angel De Pedro and Uli Schwarz
Proceedings of the National Academy of Sciences of the United States of America
Vol. 78, No. 9, [Part 2: Biological Sciences] (Sep., 1981), pp. 5856-5860
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/11568
Page Count: 5
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In vivo studies of murein biosynthesis show that newly synthesized murein unexpectedly differs in its chemical composition from preexisting murein. New murein is loosely crosslinked with the preexisting sacculus; in a maturation process involving further transpeptidation, the final stage of crosslinkage in murein is achieved. Newly inserted murein initially carries pentapeptide subunits, which are the donor of the secondary transpeptidation reaction. In mutants with defective penicillin-binding protein 4 the secondary transpeptidation step is abolished. Uncoupling of the secondary transpeptidation reaction from crosslink formation during the initial insertion of new murein was also found in a mutant with a defect in lipoprotein biosynthesis. We conclude that the initial transpeptidation of murein and crosslink formation during the maturation of newly inserted murein are catalyzed by two different enzyme systems.
Proceedings of the National Academy of Sciences of the United States of America © 1981 National Academy of Sciences