title: Analysis of the targeting sequences of an iron-containing superoxide dismutase (SOD) of the dinoflagellate Lingulodinium polyedrum suggests function in multiple cellular compartments.
abstract: One of the proteins targeted to the peridinin plastid of the dinoflagellate Lingulodinium polyedrum is the iron-containing superoxide dismutase (LpSOD). Like dinoflagellate plastid proteins of class II, LpSOD carries a bipartite presequence comprising a signal peptide followed by a transit peptide. Our bioinformatic studies suggest that its signal peptide is atypical, however, and that the entire presequence may function as a mitochondrial targeting signal. It is possible that LpSOD represents a new class of proteins in algae with complex plastids, which are co-targeted to the plastid and mitochondrion. In addition to the ambiguous N-terminal targeting signal, LpSOD contains a potential type-1 peroxisome-targeting signal (PTS1) located at its C-terminus. In accordance with a peroxisome localization of this dismutase, its mRNA has two in-frame AUG codons. Our bioinformatic analyses indicate that the first start codon resides in a much weaker oligonucleotide context than the second one. This suggests that synthesis of the plastid/mitochondrion-targeted and peroxisome-targeted isoforms could proceed through so-called leaky scanning. Moreover, our results show that expression of the two isoforms could be regulated by a 'hairpin' structure located between the first and second start codons.
authors.affiliation: Department of Biodiversity and Evolutionary Taxonomy, Zoological Institute, University of Wrocław, ul. Przybyszewskiego 63/77, 51-148 Wrocław, Poland. bodyl@biol.uni.wroc.pl
authors.forename: Andrzej
authors.initials: A
authors.lastname: Bodył
authors.forename: Paweł
authors.initials: P
authors.lastname: Mackiewicz
mesh_terms: D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D004141:Dinoflagellida / Q000201:enzymology* / Q000378:metabolism; D004586:Electrophoresis; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D020675:Peroxisomes / Q000378:metabolism*; D018087:Plastids / Q000378:metabolism; D014176:Protein Biosynthesis; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D021382:Protein Sorting Signals; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase