Protoporphyrinogen oxidase (PPO; EC 1.3.3.4) is the enzyme that catalyzes in the penultimate step in the heme biosynthetic pathway. Hemes are essential components of redox enzymes, such as cytochromes. Thus, a hemG mutant strain of Escherichia coli deficient in PPO is defective in aerobic respiration and grows poorly even in rich medium. By complementation with a human placental cDNA library, we were able to isolate a clone that enhanced the poor growth of such a hemG mutant strain. The clone encoded the gene for human PPO. Sequence analysis revealed that PPO consists of 477 amino acids with a calculated molecular mass of 50.8 kilodaltons. The deduced protein exhibited a high degree of homology over its entire length to the amino acid sequence of PPO encoded by the hemY gene of Bacillus subtilis. The NH-terminal amino acid sequence of the deduced PPO contains a conserved amino acid sequence that forms the dinucleotide-binding site in many flavin-containing proteins. Northern blot analysis revealed the synthesis of a 1.8-kilobase pair mRNA for PPO. A homogenate of the monkey kidney COS-1 cells that had been transfected with the cDNA had much higher PPO activity than an extract of control cells, and this activity was inhibited by acifluorfen, a specific inhibitor of PPO. Furthermore, the cDNA was expressed in vitro as 51-kilodalton protein, and after incubation with isolated mitochondria the protein was found to be located in the mitochondria, having just the same size as before, an indication that PPO is a mitochondrial enzyme and has no apparent transport-specific leader sequence.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				R. J. Hift, B. P. Davidson, C. van der Hooft, D. M. Meissner, and P. N. Meissner Plasma Fluorescence Scanning and Fecal Porphyrin Analysis for the Diagnosis of Variegate Porphyria: Precise Determination of Sensitivity and Specificity with Detection of Protoporphyrinogen Oxidase Mutations as a Reference Standard Clin. Chem., May 1, 2004; 50(5): 915 - 923. [Abstract] [Full Text] [PDF]

				X. Li, S. L. Volrath, D. B.G. Nicholl, C. E. Chilcott, M. A. Johnson, E. R. Ward, and M. D. Law Development of Protoporphyrinogen Oxidase as an Efficient Selection Marker for Agrobacterium tumefaciens-Mediated Transformation of Maize Plant Physiology, October 1, 2003; 133(2): 736 - 747. [Abstract] [Full Text] [PDF]

				M. von und zu Fraunberg, T. Nyronen, and R. Kauppinen Mitochondrial Targeting of Normal and Mutant Protoporphyrinogen Oxidase J. Biol. Chem., April 4, 2003; 278(15): 13376 - 13381. [Abstract] [Full Text] [PDF]

				L. Christiansen, A. Bygum, M. Kaehne, A. Jensen, M. Horder, and N. E. Petersen Mutation Screening of the Entire Coding Region of the Protoporphyrinogen Oxidase Gene Using Denaturing Gradient Gel Electrophoresis and Denaturing HPLC Clin. Chem., June 1, 2001; 47(6): 1115 - 1117. [Full Text] [PDF]

				F.-S. Che, N. Watanabe, M. Iwano, H. Inokuchi, S. Takayama, S. Yoshida, and A. Isogai Molecular Characterization and Subcellular Localization of Protoporphyrinogen Oxidase in Spinach Chloroplasts Plant Physiology, September 1, 2000; 124(1): 59 - 70. [Abstract] [Full Text]

				I. Lermontova and B. Grimm Overexpression of Plastidic Protoporphyrinogen IX Oxidase Leads to Resistance to the Diphenyl-Ether Herbicide Acifluorfen Plant Physiology, January 1, 2000; 122(1): 75 - 84. [Abstract] [Full Text] [PDF]

				S. Arnould, M. Takahashi, and J.-M. Camadro Acylation stabilizes a protease-resistant conformation of protoporphyrinogen oxidase, the molecular target of diphenyl ether-type herbicides PNAS, December 21, 1999; 96(26): 14825 - 14830. [Abstract] [Full Text] [PDF]

				S. Arnould and J.-M. Camadro The domain structure of protoporphyrinogen oxidase, the molecular target of diphenyl ether-type herbicides PNAS, September 1, 1998; 95(18): 10553 - 10558. [Abstract] [Full Text] [PDF]

				I. Lermontova, E. Kruse, H.-P. Mock, and B. Grimm Cloning and characterization of a plastidal and a mitochondrial isoform of tobacco protoporphyrinogen IX oxidase PNAS, August 5, 1997; 94(16): 8895 - 8900. [Abstract] [Full Text] [PDF]

				P Ponka Tissue-specific regulation of iron metabolism and heme synthesis: distinct control mechanisms in erythroid cells Blood, January 1, 1997; 89(1): 1 - 25. [Abstract] [Full Text]

				H. A. Dailey and T. A. Dailey Protoporphyrinogen Oxidase of Myxococcus xanthus J. Biol. Chem., April 12, 1996; 271(15): 8714 - 8718. [Abstract] [Full Text] [PDF]

				J.-M. Camadro and P. Labbe Cloning and Characterization of the Yeast HEM14 Gene Coding for Protoporphyrinogen Oxidase, the Molecular Target of Diphenyl Ether-type Herbicides J. Biol. Chem., April 12, 1996; 271(15): 9120 - 9128. [Abstract] [Full Text] [PDF]

				N. Watanabe, F.-S. Che, M. Iwano, S. Takayama, S. Yoshida, and A. Isogai Dual Targeting of Spinach Protoporphyrinogen Oxidase II to Mitochondria and Chloroplasts by Alternative Use of Two In-frame Initiation Codons J. Biol. Chem., June 1, 2001; 276(23): 20474 - 20481. [Abstract] [Full Text] [PDF]