Abstract
Thioredoxins (Trxs) are proteins that act as antioxidants by facilitating the reduction of other proteins and are highly conserved in all organisms. Plant H-type Trx isoforms have different structures and perform multiple functions. Previous studies have reported that the low molecular weight AtTrx-H2 acts as a disulfide reductase and the high molecular weight AtTrx-H3 functions as an oxidoreductase and a molecular chaperone. In this study, we compared the antifungal activities of Arabidopsis Trx-H2 and -H3 with engineered proteins 2N3C and 3N2C via domain-swapping between the N- and C-terminal regions of Trx-H2 and -H3. All AtTrx-H variant proteins inhibited cell growth of various pathogenic fungal strains at pH 5.2 and pH 7.2 and showed significant intracellular accumulation in the fungal cells. Interestingly, only two engineered proteins penetrated the fungal cell wall and membrane, indicating their ability to destabilize the fungal cell membrane before internalization into the cytosol. To our knowledge, this is the first study that demonstrates novel functions of plant antioxidants AtTrx-H2 and -H3 as antifungal proteins and shows their enhanced activity using the domain swapping technique.
Highlights
Thioredoxins (Trxs) are small ubiquitous proteins that participate in a wide variety of biological functions [1]
Antimicrobial peptides and proteins (AMPs) including host defense molecules have been widely identified in vertebrates and invertebrates, and extensively investigated as antimicrobial agents against pathogenic microorganisms, especially drug-resistant microorganisms [21]
Among the several subgroups of AtTrx, including Trx-m, -f, -x, -y, -z, -o, and -h, the most abundant H-type AtTrxs have been extensively studied for their disulfide reductase activity and use as a molecular chaperone [11]
Summary
Thioredoxins (Trxs) are small ubiquitous proteins that participate in a wide variety of biological functions [1]. Several subgroups of Trxs, including Trx-m, -f, -x, -y, -z, -o, and -h are found in Arabidopsis thaliana [2]. Trx H-type proteins are the most abundant Trx proteins in A. thaliana and can perform multiple functions, such as redox regulation, antifungal activity, and chaperone functions, in various organisms [3,4,5,6,7]. Trx proteins contain a common motif ‘Trx-fold’ with a conserved active site sequence Trp-Cys-Gly-Pro-Cys (WCGPC) or Trp-Cys-Pro-Pro-Cys (WCPPC) [10]. As AtTrx-H2 and AtTrx-H3 contain two different active site motifs—WCGPC and WCPPC, respectively—their functions and structures are substantially different [11]
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