Subcellular Localization of a Plant Catalase-Phenol Oxidase, AcCATPO, from Amaranthus and Identification of a Non-canonical Peroxisome Targeting Signal.

Ning Chen,Xiao-Lu Teng,Xing-Guo Xiao

doi:10.3389/fpls.2017.01345

Ning Chen, Xiao-Lu Teng + Show 1 more

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https://doi.org/10.3389/fpls.2017.01345

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Journal: Frontiers in Plant Science	Publication Date: Aug 2, 2017
Citations: 17	License type: cc-by

Affiliation: China Agricultural University

Abstract

AcCATPO is a plant catalase-phenol oxidase recently identified from red amaranth. Its physiological function remains unexplored. As the starting step of functional analysis, here we report its subcellular localization and a non-canonical targeting signal. Commonly used bioinformatics programs predicted a peroxisomal localization for AcCATPO, but failed in identification of canonical peroxisomal targeting signals (PTS). The C-terminal GFP tagging led the fusion protein AcCATPO-GFP to the cytosol and the nucleus, but N-terminal tagging directed the GFP-AcCATPO to peroxisomes and nuclei, in transgenic tobacco. Deleting the tripeptide (PTM) at the extreme C-terminus almost ruled out the peroxisomal localization of GFP-AcCATPOΔ3, and removing the C-terminal decapeptide completely excluded peroxisomes as the residence of GFP-AcCATPOΔ10. Furthermore, this decapeptide as a targeting signal could import GFP-10aa to the peroxisome exclusively. Taken together, these results demonstrate that AcCATPO is localized to the peroxisome and the nucleus, and its peroxisomal localization is attributed to a non-canonical PTS1, the C-terminal decapeptide which contains an internal SRL motif and a conserved tripeptide P-S/T-I/M at the extreme of C-terminus. This work may further the study as to the physiological function of AcCATPO, especially clarify its involvement in betalain biosynthesis, and provide a clue to elucidate more non-canonic PTS.

Highlights

Catalases (EC 1.11.1.6) are highly conserved metalloenzymes that are present in all aerobic and many anaerobic organisms, including bacteria, fungi, plants, and animal cells (Mueller et al, 1997; Engel et al, 2006; Kocabas et al, 2008; Mhamdi et al, 2010; Zhang et al, 2016)
A peroxisomal localization of AcCATPO was forecasted by all integrators programs except UniProt, which did not contain any information on this protein (Table 2 and Supplementary Table S1)
These prediction results implied that the AcCATPO might have some ways different from known canonical peroxisomal targeting signal (PTS, including PTS1 and PTS2) to target to peroxisomes

Summary

Introduction

Catalases (EC 1.11.1.6) are highly conserved metalloenzymes that are present in all aerobic and many anaerobic organisms, including bacteria, fungi, plants, and animal cells (Mueller et al, 1997; Engel et al, 2006; Kocabas et al, 2008; Mhamdi et al, 2010; Zhang et al, 2016). Subcellular Compartment of Plant CATPO prosthetic groups, and the diversity of sequence groups (Zámocký and Koller, 1999; Kocabas et al, 2009), namely (1) monofunctional heme-containing catalases (typical), (2) bifunctional heme-containing catalase-peroxidases, (3) manganese catalases (non-heme-containing catalases), and (4) minor catalases with slight catalytic activities. Their most important function is the decomposition of hydrogen peroxide (H2O2) into dioxygen and water (Goldberg and Hochman, 1989; Bhaskar and Poulos, 2005; Zámocký et al, 2008; Yuzugullu et al, 2013). Unlike microbial and mammalian CATPOs, this plant CATPO (AcCATPO) exhibited both monophenolase activity toward L-tyrosine and diphenolase activity toward L-3,4-dihydroxyphenylalanine (L-DOPA), in addition to the classical catalase activity toward H2O2, i.e., catalase-tyrosinase activity

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