Disease relevance of proB

• The corresponding gene of Enterobacter cloacae was transferred to E. coli K-12 by using RP4::mini Mu plasmid pULB113 and selecting for R-prime plasmids that carry the genes proA and proB, which are closely linked to phoE in E. coli K-12 [1].
• To produce the artificial bifunctional enzyme gamma-glutamyl kinase/gamma-glutamyl phosphate reductase, a mutant library of the proBA fusion gene from Bacillus subtilis was created by error-prone PCR [2].
• Enhanced and feedback-resistant gamma-glutamyl kinase activity of an Escherichia coli transformant carrying a mutated proB gene of Streptococcus thermophilus [3].

High impact information on proB

• The Vigna P5CS enzyme activity is feedback regulated by proline but is less sensitive to end-product inhibition than is the E. coli gamma-glutamyl kinase [4].
• Nucleotide sequence analysis of the proBA locus allowed gene assignments consistent with the NH2 and COOH-terminal analyses and amino acid compositions of homogeneous preparations of the proB and proA proteins [5].
• 2. Differential utilization of proline and 1-pyrroline-5-carboxylate by the proB cells for the synthesis of protein, and failure of the method to distinguish between these two possible products of the proline-biosynthetic enzymes, might also give rise to error [6].
• Comparison of the amino acid sequence of T. thermophilus gamma-glutamyl kinase with those of E. coli and S. marcescens mutants revealed that the DHP resistance mutations occurred in the amino acids conserved among the three organisms [7].
• A proB mutant has a pleiotropic phenotype, being both proline auxotrophic and affected in cell morphology [8].

Chemical compound and disease context of proB

• The proline biosynthetic genes of C. jejuni are not located tandemly and thus differ in this respect from those of E. coli and S. marcescens, where gamma-glutamyl phosphate reductase and gamma-glutamyl kinase (proB) are located in a single operon [9].
• Characteristics of the enzyme were compared with those of a gamma-glutamyl kinase partially purified from a 3,4-dehydroproline-sensitive E. coli [10].
• [Gene 39 (1984) 109-112] determined that another proB mutation (designated as DHPR), that resulted in a loss of allosteric inhibition by proline of the E. coli gamma-glutamyl kinase, was due to a substitution of an alanine for a glutamate at aa residue 143 [11].
• We used a PCR-based method to generate a single base pair mutation in the proB gene of Streptococcus thermophilus, which replaced an aspartic acid with a glycine residue at position 192 of the first proline biosynthetic enzyme gamma-glutamyl kinase [3].

Biological context of proB

• Gamma-delta insertion mutagenesis of this subcloned fragment indicated that proB and proA genes of V. parahaemolyticus might be transcribed from different promoters [12].
• The proB and proA genes, closely linked in most bacteria, are in C. glutamicum separated by a 304-amino-acid open reading frame (unk) whose predicted sequence resembles that of the 2-hydroxy acid dehydrogenases [8].
• The mutation, designated as proB74, is an allele of the Escherichia coli proB gene which results in a loss of allosteric regulation of the protein product, gamma-glutamyl kinase [11].
• Plots of gamma-glutamyl kinase activity as a function of glutamate concentration were sigmoidal, with a half-saturation value for glutamate of 33 mM, whereas plots of enzyme activity as a function of ATP concentration displayed typical Michaelis-Menten kinetics with a Km for ATP of 4 X 10(-4) M [10].
• Therefore, even though both the DHPR and the proB74 mutations caused a loss of allosteric inhibition of gamma-glutamyl kinase, they are due to different amino acid substitutions [11].

Associations of proB with chemical compounds

• However, the capacity of glutamate-gamma-semialdehyde dehydrogenase from the osmotolerant mutant to interact with the kinase was altered in thermal stability, suggesting that mutations in both proB and proA may be required for osmotolerance [13].
• While a 3.9 kb fragment which complemented proA also complemented proB, a 15 kb fragment complementing leuB could not complement other leu mutations [14].
• When speF (which encodes ornithine decarboxylase) and proB (which encodes gamma-glutamyl kinase) were inactivated to prevent the conversion of L: -ornithine to putrescine and to block the biosynthesis of a side branch of L: -ornithine, respectively, L: -ornithine production was further enhanced approxi [15].

Other interactions of proB

• Subcloning showed that about 3.1 kilobases of V. parahaemolyticus DNA could complement proA and proB but not proC mutations of Escherichia coli [12].

Analytical, diagnostic and therapeutic context of proB

• For eliminating the feedback inhibition, we first constructed a DHP-resistant mutant, TH401, by site-directed mutagenesis at the proB gene as reported for the proline-producing mutant of S. marcescens [7].

References