The murI gene of Escherichia coli is an essential gene that encodes a glutamate racemase activity.
The murI gene of Escherichia coli was recently identified on the basis of its ability to complement the only mutant requiring D-glutamic acid for growth that had been described to date: strain WM335 of E. coli B/r (P. Doublet, J. van Heijenoort, and D. Mengin-Lecreulx, J. Bacteriol. 174:5772-5779, 1992). We report experiments of insertional mutagenesis of the murI gene which demonstrate that this gene is essential for the biosynthesis of D-glutamic acid, one of the specific components of cell wall peptidoglycan. A special strategy was used for the construction of strains with a disrupted copy of murI, because of a limited capability of E. coli strains grown in rich medium to internalize D-glutamic acid. The murI gene product was overproduced and identified as a glutamate racemase activity. UDP-N-acetylmuramoyl-L-alanine (UDP-MurNAc-L-Ala), which is the nucleotide substrate of the D-glutamic-acid-adding enzyme (the murD gene product) catalyzing the subsequent step in the pathway for peptidoglycan synthesis, appears to be an effector of the racemase activity.
Doublet
P
P
URA 1131 du Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud, Orsay, France.
van Heijenoort
J
J
Bohin
J P
JP
Mengin-Lecreulx
D
D
D000591:Amino Acid Isomerases / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D002473:Cell Wall / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D005798:Genes, Bacterial / Q000235:genetics*; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010457:Peptidoglycan / Q000235:genetics / Q000378:metabolism; D013237:Stereoisomerism; D014161:Transduction, Genetic; D014538:Uridine Diphosphate N-Acetylmuramic Acid / Q000031:analogs & derivatives / Q000378:metabolism
D005971:Glutamates; D010457:Peptidoglycan; D014538:Uridine Diphosphate N-Acetylmuramic Acid; C076606:UDP-N-acetylmuramylalanine; D018698:Glutamic Acid; D000591:Amino Acid Isomerases; C062292:glutamate racemase