Disease relevance of murI

• The complementation of an auxotrophic E. coli B/r strain by various DNA sources allowed us to clone a 2.5-kbp EcoRI chromosomal fragment carrying the murI gene into multicopy plasmids [1].
• Isolation of the murI gene from Brevibacterium lactofermentum ATCC 13869 encoding D-glutamate racemase [2].
• The amino acid sequence of glutamate racemase of Lactobacillus fermenti recently reported also shows a homology with the deduced amino acid sequence of ORFI (Gallo, K. A., and Knowles, J. R. (1993) Biochemistry 32, 3981-3990) [3].
• We found that the amino acid sequence of protein deduced from the nucleotide sequence of the open reading frame of murI gene (ORF1) shows a significant homology with that of glutamate racemase of Pediococcus pentosaceus [3].
• Staphylococcus haemolyticus contains two D-glutamic acid biosynthetic activities, a glutamate racemase and a D-amino acid transaminase [4].

High impact information on murI

• Almost all bacteria possess glutamate racemase to synthesize d-glutamate as an essential component of peptidoglycans in the cell walls [5].
• In the Escherichia coli JM109/pGR3 clone, the overproducer of glutamate racemase, the copy number (i.e. replication efficiency) of plasmid DNA declined dramatically, whereas the E. coli WM335 mutant that is defective in the gene of glutamate racemase showed little genetic competency [5].
• Furthermore, we found that the DNA gyrase of E. coli was modulated by the glutamate racemase of E. coli in the presence of UDP-N-acetylmuramyl-l-alanine, which is a peptidoglycan precursor and functions as an absolute activator for the racemase [5].
• Glutamate racemase is an endogenous DNA gyrase inhibitor [5].
• The enforced production of glutamate racemase, however, resulted in suppression of cell proliferation [5].

Chemical compound and disease context of murI

• Identification of the Escherichia coli murI gene, which is required for the biosynthesis of D-glutamic acid, a specific component of bacterial peptidoglycan [1].
• It could be demonstrated for a glutamate racemase from Lactobacillus fermentii, expressed in Escherichia coli, serving as model enzyme, that its activity can be determined from the time-dependent change of the optical rotation using l-glutamate as substrate [6].
• The glutamate racemase activity from Escherichia coli is regulated by peptidoglycan precursor UDP-N-acetylmuramoyl-L-alanine [7].

Biological context of murI

• The murI gene of Escherichia coli, whose inactivation results in the inability to form colonies in the absence of D-glutamic acid, was identified in the 90-min region of the chromosome [1].
• The murI gene corresponds to a previously sequenced open reading frame, ORF1 (J. Brosius, T. J. Dull, D. D. Sleeter, and H. F. Noller. J. Bacteriol. 148:107-127, 1987), located between the btuB gene, encoding the vitamin B12 outer membrane receptor protein, and the rrnB operon, which contains the genes for 16S, 23S, and 5S rRNAs [1].
• 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 [8].
• The murI gene of Escherichia coli is an essential gene that encodes a glutamate racemase activity [8].
• The murI (dga) gene was ligated into a plasmid, pKK223-3, with a designed ribosome binding site and expressed in E. coli JM109 cells [3].

Anatomical context of murI

• A host cell line, E. coli WM335 delta recA, containing a nonfunctional chromosomal dga gene was used to minimize the background interference [9].
• Glutamate racemase was overproduced in the clone cells and occurred in inclusion bodies in the cells [10].

Associations of murI with chemical compounds

• Cells altered in the murI gene accumulate UDP-N-acetylmuramyl-L-alanine to a high level when depleted of D-glutamic acid [1].
• Investigations into the cofactor dependence of glutamate racemase indicate that the enzyme employs neither pyridoxal phosphate nor a pyruvoyl group in the labilization of the proton at the stereogenic center of glutamate [11].
• Because the two cysteine residues in glutamate racemase and their surrounding regions are well-conserved in both of these sequences, and since glutamate racemase is stabilized by the presence of reduced thiols, these residues are possible candidates for the enzymic bases that deprotonate glutamate at C-2 [11].
• Glutamate racemase catalyzes the reversible reaction of L-glutamate to D-glutamate, an essential component of the bacterial cell wall [12].
• Glutamate racemase from Aquifex pyrophilus has been crystallized by the hanging-drop vapor-diffusion method using polyethylene glycol 6000 as a precipitant [12].

Other interactions of murI

• To construct D-glutamate auxotrophs, it is necessary to transfer sequentially the mutated gltS locus, and then the mutated dga locus into the recipient [13].

Analytical, diagnostic and therapeutic context of murI

• Molecular cloning, expression, and characterization of a thermostable glutamate racemase from a hyperthermophilic bacterium, Aquifex pyrophilus [14].
• Regulation of the glutamate racemase of Escherichia coli investigated by site-directed mutagenesis [15].
• Crystallization and preliminary x-ray analysis of glutamate racemase from Aquifex pyrophilus, a hyperthermophilic bacterium [12].

References