title: L-glyceraldehyde 3-phosphate reductase from Escherichia coli is a heme binding protein.
abstract: Recently, we reported that YghZ from Escherichia coli functions as an efficient L-glyceraldehyde 3-phosphate reductase (Gpr). Here we show that Gpr co-purifies with a b-type heme cofactor. Gpr associates with heme in a 1:1 stoichiometry to form a complex that is characterized by a K(d) value of 5.8+/-0.2 microM in the absence of NADPH and a K(d) value of 11+/-1.3 microM in the presence of saturating NADPH. The absorbance spectrum of reconstituted Gpr indicates that heme is bound in a hexacoordinate low-spin state under both oxidizing and reducing conditions. The physiological function of heme association with Gpr is unclear, as the L-glyceraldehyde 3-phosphate reductase activity of Gpr does not require the presence of the cofactor. Bioinformatics analysis reveals that Gpr clusters with a family of putative monooxygenases in several organisms, suggesting that Gpr may act as a heme-dependent monooxygenase. The discovery that Gpr associates with heme is interesting because Gpr shares 35% amino acid identity with the mammalian voltage-gated K+ channel beta-subunit, an NADPH-dependent oxidoreductase that endows certain voltage-gated K+ channels with hemoprotein-like, O2-sensing properties. To date the molecular origin of O2 sensing by voltage-gated K+ channels is unknown and the results presented herein suggest a role for heme in this process.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4390, USA.
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Desai
authors.forename: Brian G
authors.initials: BG
authors.lastname: Miller
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000737:chemistry* / Q000235:genetics; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D006418:Heme / Q000737:chemistry; D000081062:Heme-Binding Proteins; D006420:Hemeproteins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D051637:Shaker Superfamily of Potassium Channels
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; C498948:KCNAB2 protein, human; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins; D051637:Shaker Superfamily of Potassium Channels; D006418:Heme; D000445:Aldehyde Oxidoreductases; C548925:L-glyceraldehyde 3-phosphate reductase, E coli