Two Unusual Amino Acid Substitutions in Cytochrome b of the Colorless AlgaPolytomellaspp.: Correlation with the Atypical Spectral Properties of the bHHeme

Antaramián, Anaid; Funes, Soledad; Vázquez-Acevedo, Miriam; Atteia, Ariane; Coria, Roberto; González‐Halphen, Diego

doi:10.1006/abbi.1998.0680

Cited by 7 publications

(3 citation statements)

References 46 publications

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“…Mitochondrial cytochromes in Polytomella sp. have been extensively characterized (1,2,19,38,39,52). In contrast, there is no evidence to date for cytochromes or other hemoproteins in the amyloplasts.…”

Section: Discussionmentioning

confidence: 99%

Enzymes of the Heme Biosynthetic Pathway in the Nonphotosynthetic Alga Polytomella sp

2005

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Heme biosynthesis involves a number of enzymatic steps which in eukaryotes take place in different cell compartments. Enzyme compartmentalization differs between photosynthetic and nonphotosynthetic eukaryotes. Here we investigated the structures and subcellular localizations of three enzymes involved in the heme pathway in Polytomella sp., a colorless alga evolutionarily related to the green alga Chlamydomonas reinhardtii. Functional complementation of Escherichia coli mutant strains was used to isolate cDNAs encoding three heme biosynthetic enzymes, glutamate-1-semialdehyde aminotransferase, protoporphyrinogen IX oxidase, and ferrochelatase. All three proteins show highest similarity to their counterparts in photosynthetic organisms, including C. reinhardtii. All three proteins have N-terminal extensions suggestive of intracellular targeting, and immunoblot studies indicate their enrichment in a dense cell fraction that is enriched in amyloplasts. These results suggest that even though the plastids of Polytomella sp. are not photosynthetically active, they are the major site of heme biosynthesis. The presence of a gene for glutamate-1-semialdehyde aminotransferase suggests that Polytomella sp. uses the five-carbon pathway for synthesis of the heme precursor 5-aminolevulinic acid.

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Section: Discussionmentioning

confidence: 99%

Enzymes of the Heme Biosynthetic Pathway in the Nonphotosynthetic Alga Polytomella sp

2005

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“…The absence of both a cell wall and thylakoid membranes in Polytomella has facilitated the purification of mitochondrial respiratory proteins and therefore made this an attractive taxon for mitochondrial studies (Gutiérrez-Cirlos et al 1994;Atteia, Dreyfus, and González-Halphen 1997). Sequences have been reported for the mitochondrial genes, cox1 and cob, from Polytomella strain SAG 198.80 (Antaramian et al 1996(Antaramian et al , 1998.…”

Section: Introductionmentioning

confidence: 99%

Mitochondrial Genome of the Colorless Green Alga Polytomella parva: Two Linear DNA Molecules with Homologous Inverted Repeat Termini

Fan

Lee

2002

Molecular Biology and Evolution

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Most of the well-characterized mitochondrial genomes from diverse green algal lineages are circular mapping DNA molecules; however, Chlamydomonas reinhardtii has a linear 15.8 kb unit mitochondrial genome with 580 or 581 bp inverted repeat ends. In mitochondrial-enriched fractions prepared from Polytomella parva (=P. agilis), a colorless, naturally wall-less relative of C. reinhardtii, we have detected two linear mitochondrial DNA (mtDNA) components with sizes of 13.5 and 3.5 kb. Sequences spanning 97% and 86% of the 13.5- and 3.5-kb mtDNAs, respectively, reveal that these molecules contain long, at least 1.3 kb, homologous inverted repeat sequences at their termini. The 3.5-kb mtDNA has only one coding region (nad6), the functionality of which is supported by both the relative rate at which it has accumulated nonsynonymous nucleotide substitutions and its absence from the 13.5-kb mtDNA which encodes nine genes (i.e., large and small subunit rRNA [LSU and SSU rRNA] genes, one tRNA gene, and six protein-coding genes). On the basis of DNA sequence data, we propose that a variant start codon, GTG, is utilized by the P. parva 13.5-kb mtDNA-encoded gene, nad5. Using the relative rate test with Chlamydomonas moewusii (=C. eugametos) as the outgroup, we conclude that the nonsynonymous nucleotide substitution rate in the mitochondrial protein-coding genes of P. parva is on an average about 3.3 times that of the C. reinhardtii counterparts.

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“…Recent molecular and biochemical data on several key proteins of the mitochondrial respiratory chain and the ATP synthase of the colorless alga Polytomella spp. and the photosynthetic alga Chlamydomonas reinhardtii have strengthened the hypothesis of Round [4–7].…”

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Polytomella spp. growth on ethananol

Atteia¹,

Lis

Ramı́rez

et al. 2000

European Journal of Biochemistry

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A defined medium with ethanol as sole carbon source was devised for growth of the colorless, unicellular alga Polytomella spp. Cell density on this carbon source was related to extracellular pH. An acidic pH was required for ethanol utilization; best yields were obtained at pH 3.7. Spectroscopic analysis of the cells showed that the concentration of cytochrome c per cell was 40% higher than at pH 6.0; the concentrations of cytochrome a 606 (cytochrome c oxidase) and b 566 (cytochrome bc 1 complex) were the same. A soluble cytochrome c 550 was purified from cells grown at pH 3.7 and characterized by peptide sequencing as the 12-kDa cytochrome c 550 of the mitochondrial respiratory chain. Immunoblots of total cell proteins showed higher accumulation of cytochrome c 550 at pH 3.7 than at pH 6.0. RNA blot analysis gave clear evidence of the abundance of c 550 transcript in cells grown at pH 3.7. The amount of mitochondrial proteins obtained from cells grown at pH 3.7 was twofold higher than that of cells grown at pH 6.0. Mitochondria isolated from both cell types readily oxidized succinate, malate or ethanol. The rates of oxygen uptake were 20±25% higher in mitochondria from cells grown at pH 3.7. Cyanide and antimycin A inhibited respiration with succinate up to 95% in both types of mitochondria. The participation of cytochrome c 550 in mitochondrial electron transport from succinate to oxygen was shown by spectral measurements.

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Two Unusual Amino Acid Substitutions in Cytochrome b of the Colorless AlgaPolytomellaspp.: Correlation with the Atypical Spectral Properties of the bHHeme

Cited by 7 publications

References 46 publications

Enzymes of the Heme Biosynthetic Pathway in the Nonphotosynthetic Alga Polytomella sp

Enzymes of the Heme Biosynthetic Pathway in the Nonphotosynthetic Alga Polytomella sp

Mitochondrial Genome of the Colorless Green Alga Polytomella parva: Two Linear DNA Molecules with Homologous Inverted Repeat Termini

Polytomella spp. growth on ethananol

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