Control of hemA expression in Rhodobacter sphaeroides 2.4.1: effect of a transposon insertion in the hbdA gene.
The common precursor to all tetrapyrroles is 5-aminolevulinic acid (ALA), and in Rhodobacter sphaeroides its formation occurs via the Shemin pathway. ALA synthase activity is encoded by two differentially regulated genes in R. sphaeroides 2.4.1: hemA and hemT. In our investigations of hemA regulation, we applied transposon mutagenesis under aerobic conditions, followed by a selection that identified transposon insertion mutants in which hemA expression is elevated. One of these mutants has been characterized previously (J. Zeilstra-Ryalls and S. Kaplan, J. Bacteriol. 178:985-993, 1996), and here we describe our analysis of a second mutant strain. The transposon inserted into the coding sequences of hbdA, coding for S-(+)-beta-hydroxybutyryl-coenzyme A dehydrogenase and catalyzing an NAD-dependent reaction. We provide evidence that the hbdA gene product participates in polyhydroxybutyrate (PHB) metabolism and, based on our findings, we discuss possibilities as to how defective PHB metabolism might alter the level of hemA expression.
Fales
L
L
Department of Biological Sciences, Oakland University, Rochester, Michigan 48309, USA.
Kryszak
L
L
Zeilstra-Ryalls
J
J
D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D004251:DNA Transposable Elements; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D006885:Hydroxybutyrates / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010957:Plasmids / Q000235:genetics; D012242:Rhodobacter sphaeroides / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D017422:Sequence Analysis, DNA
D004251:DNA Transposable Elements; D006885:Hydroxybutyrates; D015094:3-Hydroxyacyl CoA Dehydrogenases; C021388:3-hydroxybutyryl-CoA dehydrogenase; D000445:Aldehyde Oxidoreductases; C067282:glutamyl tRNA reductase