Open AccessControl of hemA Expression in Rhodobacter sphaeroides 2.4.1: Effect of a Transposon Insertion in the hbdA Gene
Author(s) -
Linda Fales,
Luiza Kryszak,
Jill H. Zeilstra-Ryalls
Publication year - 2001
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.183.5.1568-1576.2001
Subject(s) - rhodobacter sphaeroides , transposon mutagenesis , biology , transposable element , mutant , gene , mutagenesis , biochemistry , polyhydroxybutyrate , coding region , genetics , microbiology and biotechnology , bacteria
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.