Affiliation:
1. Marine and Highland Bioscience Center, Saga University, Karatsu, Saga 847-0021, Japan
Abstract
ABSTRACT
A novel antifungal protein (SAP) was found in the culture supernatant of a marine bacterium,
Streptomyces
sp. strain AP77, and was purified. This protein was characterized by chemical, biochemical, and biological analyses. By using gel filtration, the molecular mass of SAP was estimated to be 160 kDa. Structural analysis of SAP by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization-time of flight mass spectrometry suggested that SAP is composed of three heterologous protein subunits of 41.7 kDa (SAP1), 21.7 kDa (SAP2), and 18.7 kDa (SAP3) at a molar ratio of 1:1:5 (or 1:1:6). N-terminal amino acid sequence analysis and a homology search revealed that SAP1, SAP2, and SAP3 exhibit 64.3, 68.4, and 86.7% similarity to three
Streptomyces coelicolor
polypeptides, puromycin resistance protein (Pur8), a conserved hypothetical protein, and bacterioferritin, respectively. The MIC of purified SAP against
Pythium porphyrae
was determined to be 1.6 μg/disk, whereas no inhibitory effect was observed at concentrations up to 100 μg/disk against most of the fungal and bacterial strains tested; the only exception was relatively strong antifungal activity against
Pythium ultimum
(MIC, 6.3 μg/disk). In vitro and in vivo toxicity tests demonstrated that SAP showed no toxicity against
Porphyra yezoensis
cells, human normal dermal fibroblasts, and mice at doses up to 700 μg/ml (for 24 h), 250 μg/ml (for 12 h), and 75 mg/kg (for 35 days), respectively. SAP was labile when it was subjected to a heated-air drying treatment, which is a great advantage in food production procedures. These results indicated that
Streptomyces
sp. strain AP77 might be useful as a gene source for safe transgenic
Porphyra
breeding for tolerance to
Pythium
infection.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
42 articles.
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