title: Chloroplast-encoded serotonin N-acetyltransferase in the red alga Pyropia yezoensis: gene transition to the nucleus from chloroplasts.
abstract: Melatonin biosynthesis involves the N-acetylation of arylalkylamines such as serotonin, which is catalysed by serotonin N-acetyltransferase (SNAT), the penultimate enzyme of melatonin biosynthesis in both animals and plants. Here, we report the functional characterization of a putative N-acetyltransferase gene in the chloroplast genome of the alga laver (Pyropia yezoensis, formerly known as Porphyra yezoensis) with homology to the rice SNAT gene. To confirm that the putative Pyropia yezoensis SNAT (PySNAT) gene encodes an SNAT, we cloned the full-length chloroplastidic PySNAT gene by PCR and purified the recombinant PySNAT protein from Escherichia coli. PySNAT was 174 aa and had 50% amino acid identity with cyanobacteria SNAT. Purified recombinant PySNAT showed a peak activity at 55 °C with a K m of 467 µM and V max of 28 nmol min-1 mg(-1) of protein. Unlike other plant SNATs, PySNAT localized to the cytoplasm due to a lack of N-terminal chloroplast transit peptides. Melatonin was present at 0.16ng g(-1) of fresh mass but increased during heat stress. Phylogenetic analysis of the sequence suggested that PySNAT has evolved from the cyanobacteria SNAT gene via endosymbiotic gene transfer. Additionally, the chloroplast transit peptides of plant SNATs were acquired 1500 million years ago, concurrent with the appearance of green algae.
authors.affiliation: Department of Biotechnology, Interdisciplinary Program of Bioenergy and Biomaterials, Bioenergy Research Center, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, Republic of Korea.
authors.forename: Yeong
authors.initials: Y
authors.lastname: Byeon
authors.affiliation: Department of Biotechnology, Interdisciplinary Program of Bioenergy and Biomaterials, Bioenergy Research Center, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, Republic of Korea.
authors.forename: Hyoung
authors.initials: H
authors.lastname: Yool Lee
authors.affiliation: Department of Biology Education, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors.forename: Dong-Woog
authors.initials: DW
authors.lastname: Choi
authors.affiliation: Department of Biotechnology, Interdisciplinary Program of Bioenergy and Biomaterials, Bioenergy Research Center, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, Republic of Korea kback@chonnam.ac.kr.
authors.forename: Kyoungwhan
authors.initials: K
authors.lastname: Back
mesh_terms: D020418:Algal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D047068:Arylalkylamine N-Acetyltransferase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000235:genetics; D002736:Chloroplasts / Q000235:genetics; D008550:Melatonin / Q000378:metabolism*; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000461:Rhodophyta / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D020418:Algal Proteins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D047068:Arylalkylamine N-Acetyltransferase; D008550:Melatonin
keywords: Endosymbiosis; Pyropia; laver; melatonin; red algae; serotonin N-acetyltransferase