title: Expression of the heme biosynthetic pathway genes hemCD, hemH, hemM, and hemA of Escherichia coli.
abstract: Little is known about the control of latter steps of heme biosynthesis in Escherichia coli. In this study we examined the transcriptional regulation of genes that encode two intermediate heme pathway enzymes, porphobilinogen deaminase (hemC) and uroporphyrinogen III cosynthase (hemD), and the final enzyme of the pathway, ferrochelatase (hemH). We also reexamined the regulation of hemA and the gene located immediately upstream of hemA, hemM. The regulatory regions of hemC, hemH, hemA and hemM were fused to lacZ. The resultant operon fusions were inserted into the E. coli chromosome in single copy and expression monitored under conditions of oxygen and heme limitation. Expression of hemM appeared constitutive under the conditions tested here. In contrast, expression of hemCD, hemH and hemA were shown to be mildly regulated in response to heme availability. Thus, transcription of four of the nine genes of the E. coli heme pathway appears to be only mildly regulated in response to heme limitation.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90095-1489, USA.
authors.forename: P M
authors.initials: PM
authors.lastname: McNicholas
authors.forename: G
authors.initials: G
authors.lastname: Javor
authors.forename: S
authors.initials: S
authors.lastname: Darie
authors.forename: R P
authors.initials: RP
authors.lastname: Gunsalus
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics; D002244:Carbon / Q000378:metabolism; D002352:Carrier Proteins; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005294:Ferrochelatase / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006418:Heme / Q000096:biosynthesis* / Q000235:genetics*; D011163:Hydroxymethylbilane Synthase / Q000235:genetics; D007763:Lac Operon; D018832:Molecular Chaperones; D009566:Nitrates / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D014576:Uroporphyrinogen III Synthetase / Q000235:genetics
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C087012:LolB protein, E coli; D018832:Molecular Chaperones; D009566:Nitrates; D006418:Heme; D002244:Carbon; D000445:Aldehyde Oxidoreductases; C067282:glutamyl tRNA reductase; D011163:Hydroxymethylbilane Synthase; C073160:hemC protein, E coli; D014576:Uroporphyrinogen III Synthetase; D005294:Ferrochelatase; D010100:Oxygen