ISSN:
1617-4623
Keywords:
Key words Heme biosynthesis
;
5-aminolevulinic acid dehydratase
;
hemB
;
Metal dependence
;
Pseudomonas aeruginosa
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract During tetrapyrrole biosynthesis 5-aminolevulinic acid dehydratase (ALAD) catalyzes the condensation of two molecules of 5-aminolevulinic acid (ALA) to form one molecule of the pyrrole derivative porphobilinogen. In Escherichia coli, the enzyme is encoded by the gene hemB. The hemB gene was cloned from Pseudomonas aeruginosa by functional complementation of an E. coli hemB mutant. An open reading frame of 1011 bp encoding a protein of 336 amino acids (Mr = 37 008) was identified. The gene was mapped to SpeI fragment G and DpnI fragment G of the P. aeruginosa chromosome, corresponding to the 10 to 12 min region of the new map or 19 to 22 min interval of the old map. The 5′ end of the hemB mRNA was determined and the −10 and −35 regions of a potential σ70-dependent promoter were localized. No obvious regulation of the hemB gene by oxygen, nitrate, heme or iron was detected. Alignment of the amino acid sequences deduced from hemB revealed a potential metal-binding site and indicated that the enzyme is Mg2+-dependent. P. aeruginosa hemB was overexpressed in an E. coli hemB mutant using the phage T7 RNA polymerase system and its Mg2+-dependent activity was directly demonstrated.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004380050673
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