Disease relevance of phoA

• The nucleotide sequence of the promoter and the amino-terminal region of alkaline phosphatase structural gene (phoA) of Escherichia coli [1].
• Some other mutations that lead to constitutive psiO expression (which is normally induced either by phosphate, nitrogen or carbon starvation or anoxia) show decreased expression of phoA [2].
• New pleiotropic mutants were isolated that express either the phoA, psiE or psiO promoter constitutively and simultaneously alter bacterial alkaline phosphatase regulation, carbon utilization or ultraviolet light sensitivity [2].
• The killing rate is increased by using a plasmid-encoded suicide system consisting of the phage T7 lysozyme gene driven by the E. coli alkaline phosphatase gene promoter (phoA) [3].
• In some, the clonal variation of the lactose phenotype or bacterial alkaline phosphatase synthesis is recA-independent and phenotypically resembles phase variation in Salmonella typhimurium [2].

High impact information on phoA

• The catalytically essential amino acid in the active site of bacterial alkaline phosphatase (Ser-102) has been replaced with a cysteine by site-directed mutagenesis [4].
• Analysis of phoA fusions with pkn2 demonstrated that Pkn2 is a transmembrane protein with the kinase domain in the cytoplasm and the 207-residue carboxy-terminal domain outside the cytoplasmic membrane [5].
• Transposon mutagenesis studies strongly suggest that BAP is the only enzyme involved in the phoA-dependent pathway [6].
• Highly purified BAP catalyzed Pt oxidation with specific activities of 62-242 milliunits/mg and phosphate ester hydrolysis with specific activities of 41-61 units/mg [6].
• A new activity for an old enzyme: Escherichia coli bacterial alkaline phosphatase is a phosphite-dependent hydrogenase [6].

Chemical compound and disease context of phoA

• Membrane topology analysis of Escherichia coli mannitol permease by using a nested-deletion method to create mtlA-phoA fusions [7].
• This rapid efficient supercoiling is observed during transcription of membrane-associated gene products, encoded by tet (the gene for tetracycline resistance) and phoA (the gene for E. coli alkaline phosphatase), when the genes are oppositely oriented [8].
• The rat liver alpha subunit, from arginine 15 to the C-terminal proline 510, has been overexpressed in Escherichia coli using the alkaline phosphatase promoter (phoA) and leader peptide to direct the export of the expressed protein to the bacterial periplasm [9].
• Amber suppressor mutagenesis, used to create mutant proteins, included: (i) introduction of amber mutations into respective positions of the phoA gene; and (ii) expression of each mutant phoA allele in E. coli strains producing amber suppressor tRNAs specific to Ala, Cys, Gln, Glu, Gly, His, Leu, Lys, Phe, Pro, Ser and Tyr [10].
• Approximately 90% of the cGSTM1-1 or rGSTT1-1 overexpressed in E. coli under the control of a phoA promoter retained the initiator methionine residue that was absent from the mature isoenzymes isolated from tissues [11].

Biological context of phoA

• Four different pulA-phoA gene fusions encoded hybrids with alkaline phosphatase activity [12].
• The promoter and the amino-terminal region of phoA, the structural gene for alkaline phosphatase of Escherichia coli K12, was cloned by using a promoter cloning vector pMC1403 [1].
• The promoter region of phoE has no homology with the consensus sequence of E. coli promoter regions, but homologous sequences with the promoter region of phoA, the structural gene for alkaline phosphatase, were observed [13].
• The sequence of an osmC-phoA gene fusion confirmed the osmC reading frame [14].
• In the regulatory region of the gene, a consensus nucleotide sequence shared by the regulatory regions of the phoA, phoS and phoE genes, which we name the "phosphate box", was found [15].

Anatomical context of phoA

• Indeed, the pattern of variation observed in BAP-variable phoR strains is phenotypically analogous to phase variation of the H1/H2 flagellum antigen type in Salmonella typhimurium and the molecular switch between the immune and sensitive states in bacteriophage lambda [16].
• Induction of the phoA promoter of pho regulon and secretion of the product to the periplasm may depress heat shock-like responses and subsequent hydrolysis of the product by cytoplasmic protease [17].
• Genetic systems for transposon mutagenesis of the L. pneumophila genome (Tn5, Tn903dIIlacZ, MudphoA), including Tn phoA shuttle mutagenesis, have been established and specifically adapted to identify mutants which displayed an impaired capability to multiply inside macrophages and with a reduced in vivo virulence [18].
• One mutant selected for its impaired ability to invade epithelial cells had an insertion of a Tn phoA transposon within the nlpI gene encoding the lipoprotein NlpI [19].
• By analyzing reciprocal fusions between crdS and the reporter genes, lacZ and phoA, and assessing the sensitivity of CrdS in spheroplasts to proteinase K, CrdS was shown to be an integral membrane protein with seven transmembrane helices and an Nout-Cin disposition [20].

Associations of phoA with chemical compounds

• The switching is regulated by the phoM operon and the presence of glucose; the pho-510 mutant form of the phoM operon abolishes both BAP clonal variation and the effect of glucose (B.L. Wanner, J. Bacteriol. 169:900-903, 1987) [21].
• Induction of malF-phoA fusion proteins, which have no significant effects on membrane integrity, did not alter susceptibility to streptomycin [22].
• Herein, the phoA promoter without its associated signal peptide is used to regulate expression of the HPRT of Schistosoma mansoni and the ornithine decarboxylase (ODC; L-ornithine carboxy-lyase, EC 4.1.1.17) of Trypanosoma brucei, two enzymes that have been identified as potential targets for antiparasitic chemotherapy [23].
• Several mtlA-phoA gene fusions encoding fused proteins with N-terminal regions derived from the mannitol permease and C-terminal regions derived from the mature portion of alkaline phosphatase were constructed [24].
• The amount of initiator methionine was decreased to 40% of the expressed cGSTM1-1 when the isoenzyme was co-expressed with an exogenous methionine aminopeptidase gene under the control of a separate phoA promoter [11].

Physical interactions of phoA

• It is negatively controlled by phoR as well as by the phosphate-specific transport (PST) system in Escherichia coli. phoA induction is positively controlled by the phoB, M, and R products; it is unaffected by the cAMP and CAP system [25].

Regulatory relationships of phoA

• However, only phoU mutants express both phoA and psiE constitutively [2].
• The alteration of DNA sequence was identified for a promoter mutation that results in the expression of phoA independent of the positive control gene phoB and in insensitivity to high phosphate [26].
• From these results we conclude that the expression of the phoA gene is not always co-regulated with expression of the phoS gene product [27].

Other interactions of phoA

• Osmo-inducible fusions of phoA were found to ompC and to a gene that is probably proU [28].
• This phenotype is clearly different from that of the previously isolated class of envZ mutants that exhibit an OmpF- OmpC+ phenotype and a pleiotropic decrease in the expression of several exported protein genes, including lamB and phoA [29].
• The alternation acted at the level of phoA transcription; it was also recA independent [30].
• The addition of the local anesthetic procaine to wild-type strains also causes a pleiotropic decrease in the expression of genes ompF, lamB, and phoA [29].
• Fusions between fhuA and phoA genes were constructed [31].

Analytical, diagnostic and therapeutic context of phoA

• Mapping and sequence analysis of the cloned phoA fusions in strains MC7 and MC19 indicated that they had occurred in different locations within the same previously unidentified gene [32].
• To examine this further, mutations within the E. coli phoA gene were created using site-directed mutagenesis [33].
• Cloning and restriction mapping of the alkaline phosphatase structural gene (phoA) of Escherichia coli and generation of deletion mutants in vitro [34].
• These results indicate that bacterially expressed scFv and scFv-BAP would be of practical use in blood typing [35].
• In addition, 3XFLAG bacterial alkaline phosphatase was expressed in Escherichia coli, purified on anti-FLAG M2 affinity gel, and detection of 500 pg of purified protein by Western blot analysis is demonstrated [36].

References