Disease relevance of algD

• A bioassay was developed to identify stimuli that promote the transcriptional induction of the algD operon for alginate biosynthesis in Pseudomonas aeruginosa [1].
• Pseudomonas aeruginosa infection in cystic fibrosis: nucleotide sequence and transcriptional regulation of the algD gene [2].
• The involvement of cAMP-CRP complex in the activation of the algD promoter in E. coli has been demonstrated directly through binding of a 255 base pair DNA fragment containing the putative consensus CRP binding sequence [3].
• Transcriptional activation of the Pseudomonas aeruginosa algD gene results in high-level synthesis of the capsular polysaccharide alginate, an important P. aeruginosa virulence factor expressed in cystic fibrosis (CF) patients with chronic pulmonary disease [4].
• Characterization of the gene coding for GDP-mannose dehydrogenase (algD) from Azotobacter vinelandii [5].

High impact information on algD

• The algU gene is required for expression of the key alginate biosynthetic gene algD and encodes a protein homologous to sigma H, an alternative sigma factor regulating sporulation and other post-exponential-phase processes in Bacillus [6].
• While the presence of at least one AlgR1 binding site is important for the activation of the algD promoter, the presence of both of the binding sites in the upstream region leads to a higher level of activation [7].
• The upstream region of the algC gene contained a sequence identical to the algD upstream sequence that is known to be the binding site for the AlgR1 protein [8].
• The enzyme was overproduced using a plasmid vector containing algD (the gene encoding this enzyme) under control of the tac promoter [9].
• The subunit molecular weight (Mr 48,000) as well as the N-terminal amino acid sequence corresponded to those predicted from the DNA sequence of algD [9].

Chemical compound and disease context of algD

• We also demonstrate that the algD promoter is sensitive to glucose repression both in E. coli and P. aeruginosa [3].
• Gene algD coding for GDPmannose dehydrogenase is transcriptionally activated in mucoid Pseudomonas aeruginosa [10].
• Pseudomonas aeruginosa produced alginate and elevated algD (encoding GDPmannose 6-dehydrogenase) transcription under strict anaerobic conditions, especially when using nitrate as a terminal electron acceptor [11].
• Inactivation of Pseudomonas aeruginosa phpA, encoding a putative leucine aminopeptidase, results in increased transcription of algD [12].
• Pattern of changes in the activity of enzymes of GDP-D-mannuronic acid synthesis and in the level of transcription of algA, algC and algD genes accompanying the loss and emergence of mucoidy in Pseudomonas aeruginosa [13].

Biological context of algD

• A transcriptome analysis using microarrays verified that the algD operon undergoes high induction by d-cycloserine [1].
• Transcriptional activation of algD was shown to be necessary for alginate production [2].
• Transcriptional activation of algD, the first gene of a large alginate biosynthetic gene cluster, is associated with conversion to the alginate-producing (Alg+) phenotype [14].
• In contrast, a PA14 algD mutant was not impaired in virulence in plants, nematodes or mice [15].
• Oligonucleotide mutagenesis was employed to create an algD allele with a 4 bp mutation in the predicted AlgZ-binding site (algD38) and a heterologous substitution allele (algD40), in which the entire AlgZ-binding site was replaced with a non-specific DNA sequence of identical size [4].

Associations of algD with chemical compounds

• Strain PAO1 carried the algD promoter fused to a chloramphenicol acetyl-transferase cartridge (PalgD-cat), and > 50 compounds were tested for promoting chloramphenicol resistance [1].
• In order to determine whether the alginate or lipopolysaccharide (LPS) defect was responsible for the avirulence of this strain, we constructed a strain with a mutation in an alginate-specific gene, algD [16].
• Deletion of a putative consensus CRP binding sequence upstream of the algD promoter renders the promoter non-responsive to glucose repression [3].
• In this report we demonstrate that ethanol (a commonly used dehydrating agent) activates transcription from a critical alginate promoter, algD, and show that prolonged exposure to ethanol allows switching to the mucoid form [17].
• The response regulators AlgB and AlgR are required for the transcription of algD, a tightly regulated gene encoding GDP-mannose dehydrogenase, which is critical for P. aeruginosa alginate biosynthesis [18].

Physical interactions of algD

• In gel band mobility shift assays, a protein(s) present in extracts from mucoid and algB and algR mutant P. aeruginosa strains formed a specific complex with algD sequences located immediately upstream of the start of transcription [18].

Regulatory relationships of algD

• Using the algD-xy1E transcriptional fusion the algD promoter was demonstrated to be under positive control by the algR gene [2].
• This result suggested that toxA was regulated independently of algD [19].

Other interactions of algD

• Transcription of algD occurred on the 4th day and increased regularly over time suggesting a balance in the transcription of exoS and algD [20].
• The algR gene product, which controls transcription of a key alginate biosynthetic gene, algD, is homologous to the activator members of the two-component, environmentally responsive systems (NtrC, OmpR, PhoB, ArcA, etc) [21].
• Northern blot hybridization experiments also showed that a transposon insertion downstream of algD adversely affected algG and algA transcription [14].
• We show that algB is transcriptionally active in mucoid strains of P. aeruginosa and regulates the expression of the alginate biosynthetic gene, algD, thereby resulting in increased expression of alginate in mucoid P. aeruginosa [22].
• When PAO568, a model strain for the analysis of control of the alginate system, was grown under conditions promoting mucoidy, the algD promoter was activated, whereas lasB mRNA could not be detected [23].

Analytical, diagnostic and therapeutic context of algD

• Electrophoretic mobility-shift assays and copper-phenanthroline footprinting localized AlgZ binding to a 36 bp algD region, which includes several helical repeats [4].
• This report describes a PCR primer pair that targets the algD GDP mannose gene of Pseudomonas aeruginosa and produces a specific 520-bp PCR product useful for P. aeruginosa identification [24].

References