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Applied and Environmental Microbiology, April 2006, p. 2407-2413, Vol. 72, No. 4
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.4.2407-2413.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Novel Hydrophobic Surface Binding Protein, HsbA, Produced by Aspergillus oryzae

Shinsaku Ohtaki,¹ Hiroshi Maeda,^2,3,5 Toru Takahashi,¹ Youhei Yamagata,^1,3 Fumihiko Hasegawa,³ Katsuya Gomi,^3,4 Tasuku Nakajima,^1,3 and Keietsu Abe^1,3*

Laboratory of Molecular Enzymology, Division of Life Science, Graduate School of Agricultural Science, Tohoku University, Sendai 985-8555, Japan,¹ Tohoku Technoarch Co., Ltd., Sendai 980-8577, Japan,² The New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan,³ Laboratory of Bioindustrial Genomics, Division of Bioscience and Biotechnology for Future Bioindustries, Graduate School of Agricultural Science, Tohoku University, Sendai 985-8555, Japan,⁴ Chiba Industrial Technology Research Institute, Chiba 264-0017, Japan⁵

Received 8 July 2005/ Accepted 19 January 2006

Hydrophobic surface binding protein A (HsbA) is a secreted protein (14.5 kDa) isolated from the culture broth of Aspergillus oryzae RIB40 grown in a medium containing polybutylene succinate-co-adipate (PBSA) as a sole carbon source. We purified HsbA from the culture broth and determined its N-terminal amino acid sequence. We found a DNA sequence encoding a protein whose N terminus matched that of purified HsbA in the A. ozyzae genomic sequence. We cloned the hsbA genomic DNA and cDNA from A. oryzae and constructed a recombinant A. oryzae strain highly expressing hsbA. Orthologues of HsbA were present in animal pathogenic and entomopathogenic fungi. Heterologously synthesized HsbA was purified and biochemically characterized. Although the HsbA amino acid sequence suggests that HsbA may be hydrophilic, HsbA adsorbed to hydrophobic PBSA surfaces in the presence of NaCl or CaCl₂. When HsbA was adsorbed on the hydrophobic PBSA surfaces, it promoted PBSA degradation via the CutL1 polyesterase. CutL1 interacts directly with HsbA attached to the hydrophobic QCM electrode surface. These results suggest that when HsbA is adsorbed onto the PBSA surface, it recruits CutL1, and that when CutL1 is accumulated on the PBSA surface, it stimulates PBSA degradation. We previously reported that when the A. oryzae hydrophobin RolA is bound to PBSA surfaces, it too specifically recruits CutL1. Since HsbA is not a hydrophobin, A. oryzae may use several types of proteins to recruit lytic enzymes to the surface of hydrophobic solid materials and promote their degradation.

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* Corresponding author. Mailing address: Laboratory of Molecular Enzymology, Department of Molecular and Cell Biology, Graduate School of Agricultural Science, Tohoku University, 1-1 Amamiya, Tsutsumi-dori, Aobaku, Sendai 981-8555, Japan. Phone: 81-22-717-8777. Fax: 81-22-717-8778. E-mail: kabe{at}biochem.tohoku.ac.jp.

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Applied and Environmental Microbiology, April 2006, p. 2407-2413, Vol. 72, No. 4
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.4.2407-2413.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.