Deficiency in L-serine deaminase interferes with one-carbon metabolism and cell wall synthesis in Escherichia coli K-12.
Escherichia coli K-12 provided with glucose and a mixture of amino acids depletes L-serine more quickly than any other amino acid even in the presence of ammonium sulfate. A mutant without three 4Fe4S L-serine deaminases (SdaA, SdaB, and TdcG) of E. coli K-12 is unable to do this. The high level of L-serine that accumulates when such a mutant is exposed to amino acid mixtures starves the cells for C(1) units and interferes with cell wall synthesis. We suggest that at high concentrations, L-serine decreases synthesis of UDP-N-acetylmuramate-L-alanine by the murC-encoded ligase, weakening the cell wall and producing misshapen cells and lysis. The inhibition by high L-serine is overcome in several ways: by a large concentration of L-alanine, by overproducing MurC together with a low concentration of L-alanine, and by overproducing FtsW, thus promoting septal assembly and also by overexpression of the glycine cleavage operon. S-Adenosylmethionine reduces lysis and allows an extensive increase in biomass without improving cell division. This suggests that E. coli has a metabolic trigger for cell division. Without that reaction, if no other inhibition occurs, other metabolic functions can continue and cells can elongate and replicate their DNA, reaching at least 180 times their usual length, but cannot divide.
Zhang
Xiao
X
Biology Department, Concordia University, 1455 de Maisonneuve Ave., Montreal, Quebec H3G 1M8, Canada.
El-Hajj
Ziad W
ZW
Newman
Elaine
E
D000409:Alanine / Q000378:metabolism; D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism; D002244:Carbon / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D048168:Escherichia coli K12 / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D005947:Glucose / Q000737:chemistry / Q000378:metabolism; D019271:Hypoxanthine / Q000378:metabolism; D012695:L-Serine Dehydratase / Q000172:deficiency*; D009154:Mutation; D011401:Promoter Regions, Genetic; D012694:Serine / Q000378:metabolism
D000596:Amino Acids; D003470:Culture Media; D029968:Escherichia coli Proteins; C017721:casamino acids; D019271:Hypoxanthine; D012694:Serine; D002244:Carbon; D012695:L-Serine Dehydratase; D005947:Glucose; D000409:Alanine