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Expression and Functional Analysis of Aminotransferase Involved in Indole-3-acetic Acid Biosynthesis in Azospirillum brasilense Yu62

Shi-Mei Ge1, Li Tao1, and San-Feng Chen1,2*

1Department of Microbiology and Immunology, College of Biological Sciences, China Agricultural University, Beijing, 100094, P. R. China; fax: 86 (106) 273-1551; E-mail: chensf@cau.edu.cn; geshme@163.com; litao_856@163.com

2College of Biological Sciences and National Key Laboratory for Agrobiotechnology, China Agricultural University, Beijing 100094, P. R. China

* To whom correspondence should be addressed.

Received May 26, 2008; Revision received June 23, 2008
In this study, atrC (a novel gene from Azospirillum brasilense identified in our laboratory) was expressed in Escherichia coli, and SDS-PAGE analysis of the expressed AtrC revealed the apparent molecular weight of 45 kD. When analyzed under non-denaturing PAGE conditions and using L-tryptophan as a substrate, the purified AtrC protein exhibited aminotransferase activity, while crude protein extracts from A. brasilense Yu62 showed two activity bands with molecular masses estimated as 44 and 66 kD. Thus, we deduced that AtrC protein is identical to the 44 kD band of crude protein extracts. The optimal temperature and pH for the catalytic activity of the purified AtrC are 30°C and pH 7.0, respectively.
KEY WORDS: function analysis, aminotransferase, Azospirillum brasilense, indole-3-acetic acid

DOI: 10.1134/S000629790901012X